VOGONS


Reply 27720 of 27960, by caejr73

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Love the display case! What material is that (the white stuff) that the processors are on? Can you hang the case on the wall? I have been thinking of doing something like this for years but have yet to make one.

Reply 27721 of 27960, by BetaC

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caejr73 wrote on 2024-06-05, 23:52:

Love the display case! What material is that (the white stuff) that the processors are on? Can you hang the case on the wall? I have been thinking of doing something like this for years but have yet to make one.

As far as I can tell it's just cotton. I think I could maybe get it up on the wall as well, but given the strength of the latch I'd rather not try it.

rfbu29-99.png
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z5lb91-6.png

Reply 27722 of 27960, by BigDave

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gerry wrote on 2024-06-03, 14:35:
BigDave wrote on 2024-06-02, 11:52:

Not technically a retro activity, but it's a rare sunny day in the UK, so perfect for a bit of Retro-Brite. First off, is my most recent computer addition, an Amstrad PCW8256, simply because I never owned or used one, so out of curiosity. The keyboard & dot matrix printer are fine, but the unit is heavily yellowed, I don't have time to dismantle, so done my usual paint on Jerome Blonde hair cream & cling film. Messy, but had good results on a Dreamcast & my VIC20's before.

vic 20's plural? sounds good, an overlooked early home computer than one, i remember them co-existing with the c64 for a while

Hi Gerry, yes, plural as in 3, and as the first computer I ever owned, I loved it! It's what I learnt to program on, using a B&W TV before getting a C64. I didn't get a VIC until well after the C64 release, late '84, so you're absolutely right, they co-existed for some time. As Dixons had reduced the VIC20 Starter Pack to £99.99 by then. Decades later, found one at a car boot, didn't work, then my Wife surprised me with complete starter pack for my birthday, but the eBay seller lied, it didn't 'fully' work, and too late to return. 3rd time lucky, bought another in better condition, and fully working.

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VIC 20, with C2N, SD2IEC & Penultimate+ cart
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I'm just a hobbyist, not a computer technician, so used that to compare, a schematic and a logic probe to help me repair No.2, a 74 logic IC, and Kernal ROM, with No.1 used for spares. I've got one setup, which I swap with a 64, and been working on a new Lingo TV game for about a year.

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Old School programming in Basic on a 3K Vic. Printout using .TAP in VICE
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Funny,40 years on still remember screen code addresses, but people's addresses? No.

Reply 27723 of 27960, by ssokolow

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I just received the Igel 3/2 thin client I ordered and answered a YouTube commenter who was wondering what key you have to press to get into the BIOS. (Hammer on the Delete key while powering on and it'll enter the BIOS after showing the "booting, please wait ..." message for a couple of seconds.)

Internet Archive: My Uploads
My Blog: Retrocomputing Resources
My Rose-Coloured-Glasses Builds

I also try to announce retro-relevant stuff on on Mastodon.

Reply 27724 of 27960, by RetroLizard

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I picked up a Micron Gobook 2 today. It cosmetically looks fine, though could use some cleaning. I'm sadly unable to test it, as I don't have a proper cable to go with it.

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Reply 27725 of 27960, by PTherapist

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BigDave wrote on 2024-06-07, 10:15:
Hi Gerry, yes, plural as in 3, and as the first computer I ever owned, I loved it! It's what I learnt to program on, using a B&W […]
Show full quote
gerry wrote on 2024-06-03, 14:35:
BigDave wrote on 2024-06-02, 11:52:

Not technically a retro activity, but it's a rare sunny day in the UK, so perfect for a bit of Retro-Brite. First off, is my most recent computer addition, an Amstrad PCW8256, simply because I never owned or used one, so out of curiosity. The keyboard & dot matrix printer are fine, but the unit is heavily yellowed, I don't have time to dismantle, so done my usual paint on Jerome Blonde hair cream & cling film. Messy, but had good results on a Dreamcast & my VIC20's before.

vic 20's plural? sounds good, an overlooked early home computer than one, i remember them co-existing with the c64 for a while

Hi Gerry, yes, plural as in 3, and as the first computer I ever owned, I loved it! It's what I learnt to program on, using a B&W TV before getting a C64. I didn't get a VIC until well after the C64 release, late '84, so you're absolutely right, they co-existed for some time. As Dixons had reduced the VIC20 Starter Pack to £99.99 by then. Decades later, found one at a car boot, didn't work, then my Wife surprised me with complete starter pack for my birthday, but the eBay seller lied, it didn't 'fully' work, and too late to return. 3rd time lucky, bought another in better condition, and fully working.
IMG_20240605_093339~2.jpg
I'm just a hobbyist, not a computer technician, so used that to compare, a schematic and a logic probe to help me repair No.2, a 74 logic IC, and Kernal ROM, with No.1 used for spares. I've got one setup, which I swap with a 64, and been working on a new Lingo TV game for about a year.
IMG_20240605_093255~2.jpg
Funny,40 years on still remember screen code addresses, but people's addresses? No.

A Lingo game actually sounds pretty cool. Are you writing that for the VIC-20 or C64?

Reply 27726 of 27960, by BigDave

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PTherapist wrote on 2024-06-08, 15:10:
BigDave wrote on 2024-06-07, 10:15:
Hi Gerry, yes, plural as in 3, and as the first computer I ever owned, I loved it! It's what I learnt to program on, using a B&W […]
Show full quote
gerry wrote on 2024-06-03, 14:35:

vic 20's plural? sounds good, an overlooked early home computer than one, i remember them co-existing with the c64 for a while

Hi Gerry, yes, plural as in 3, and as the first computer I ever owned, I loved it! It's what I learnt to program on, using a B&W TV before getting a C64. I didn't get a VIC until well after the C64 release, late '84, so you're absolutely right, they co-existed for some time. As Dixons had reduced the VIC20 Starter Pack to £99.99 by then. Decades later, found one at a car boot, didn't work, then my Wife surprised me with complete starter pack for my birthday, but the eBay seller lied, it didn't 'fully' work, and too late to return. 3rd time lucky, bought another in better condition, and fully working.
IMG_20240605_093339~2.jpg
I'm just a hobbyist, not a computer technician, so used that to compare, a schematic and a logic probe to help me repair No.2, a 74 logic IC, and Kernal ROM, with No.1 used for spares. I've got one setup, which I swap with a 64, and been working on a new Lingo TV game for about a year.
IMG_20240605_093255~2.jpg
Funny,40 years on still remember screen code addresses, but people's addresses? No.

A Lingo game actually sounds pretty cool. Are you writing that for the VIC-20 or C64?

Hi, it's for the VIC 20 + 3k, as I figured it'd be more challenging with a memory limit, and the sort of game that would work well on a VIC in Basic. I've made it for my wife, she loves the show, and seemed like a good project, but will make available when it's done.

Reply 27727 of 27960, by PTherapist

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BigDave wrote on 2024-06-08, 16:18:
PTherapist wrote on 2024-06-08, 15:10:
BigDave wrote on 2024-06-07, 10:15:
Hi Gerry, yes, plural as in 3, and as the first computer I ever owned, I loved it! It's what I learnt to program on, using a B&W […]
Show full quote

Hi Gerry, yes, plural as in 3, and as the first computer I ever owned, I loved it! It's what I learnt to program on, using a B&W TV before getting a C64. I didn't get a VIC until well after the C64 release, late '84, so you're absolutely right, they co-existed for some time. As Dixons had reduced the VIC20 Starter Pack to £99.99 by then. Decades later, found one at a car boot, didn't work, then my Wife surprised me with complete starter pack for my birthday, but the eBay seller lied, it didn't 'fully' work, and too late to return. 3rd time lucky, bought another in better condition, and fully working.
IMG_20240605_093339~2.jpg
I'm just a hobbyist, not a computer technician, so used that to compare, a schematic and a logic probe to help me repair No.2, a 74 logic IC, and Kernal ROM, with No.1 used for spares. I've got one setup, which I swap with a 64, and been working on a new Lingo TV game for about a year.
IMG_20240605_093255~2.jpg
Funny,40 years on still remember screen code addresses, but people's addresses? No.

A Lingo game actually sounds pretty cool. Are you writing that for the VIC-20 or C64?

Hi, it's for the VIC 20 + 3k, as I figured it'd be more challenging with a memory limit, and the sort of game that would work well on a VIC in Basic. I've made it for my wife, she loves the show, and seemed like a good project, but will make available when it's done.

Cool, that sounds great. I'd definitely give that a try when it's finished.

You're right, the VIC is ideal for those type of games.

I haven't got any real programming skills myself, but I did manage to compile several pieces of other people's modifications for the VIC-20 version of the BBC Mastermind quiz game (all programmed in BASIC), particularly a patch to make it more acceptable of typos. I played it with friends and I wasn't happy with the correct answer reveals after every incorrect answer, as it became just a memory game then. So I went back in to the code and made some edits so that it only reveals the answers if you pass and of course passes count against in the case of a tie. Coupled with the question editor to make your own packs, it is a really fun quiz game and only needs 8K RAM.

Reply 27728 of 27960, by liqmat

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BigDave wrote on 2024-06-08, 16:18:

Hi, it's for the VIC 20 + 3k, as I figured it'd be more challenging with a memory limit, and the sort of game that would work well on a VIC in Basic. I've made it for my wife, she loves the show, and seemed like a good project, but will make available when it's done.

Hey BigDave,

Love the VIC-20. Restored a few of them about ten years back. Never owned one as I started on a C64 in the early 80s as a teen, but fell for them in the two thousand teens. Especially the first revision models (gold label with the internal power supply). Anyway, highly recommend the 32K RAM expansion cart. This dev is a prime example of pushing the VIC to its limits >> https://huffelduff.itch.io/

and of course the amazing 2015 32K Popeye... (download in the description)
https://youtu.be/BMRFsyERpng?feature=shared

Last edited by liqmat on 2024-06-08, 18:11. Edited 1 time in total.

Reply 27729 of 27960, by DosFreak

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Took the heatsink and fan off of my HD 4870 in preperation for a replacement fan. Once done will be used with modified drivers for usage with Windows 2000 and passthrough with proxmox.

How To Ask Questions The Smart Way
Make your games work offline

Reply 27730 of 27960, by BigDave

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liqmat wrote on 2024-06-08, 17:46:
Hey BigDave, […]
Show full quote
BigDave wrote on 2024-06-08, 16:18:

Hi, it's for the VIC 20 + 3k, as I figured it'd be more challenging with a memory limit, and the sort of game that would work well on a VIC in Basic. I've made it for my wife, she loves the show, and seemed like a good project, but will make available when it's done.

Hey BigDave,

Love the VIC-20. Restored a few of them about ten years back. Never owned one as I started on a C64 in the early 80s as a teen, but fell for them in the two thousand teens. Especially the first revision models (gold label with the internal power supply). Anyway, highly recommend the 32K RAM expansion cart. This dev is a prime example of pushing the VIC to its limits >> https://huffelduff.itch.io/

and of course the amazing 2015 32K Popeye... (download in the description)
https://youtu.be/BMRFsyERpng?feature=shared

In the 80s I had a 16K RAM, but now I've got a Penultimate+ cart, so that does RAM upto 32/35k, but guessed more people these days would have either a regular switchable RAM pack, or Super Expander Cart since they're cheaper, which is also a 3K RAM pack, plus, old habits die hard!
OMG that Dev's work, WOW! it's amazing what can be squeezed out of the little VIC, I'm in total admiration of these real programmers. The Popeye game is fantastic, and was a favourite of mine in the arcades back in the day.

Reply 27731 of 27960, by NHVintage

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While I wait for EEPROM chips to show up for the 286 board from the CNC machine so I can try a standard bios on it, a new PC arrived on my doorstep: A Zenith ZDH-1111 system. And it's a mystery because I can't find docs on it or it's mobo anywhere!

It LOOKS like a Z-150 on the outside, and its an 8088 machine, but instead of having just a backplane fixed in the chassis, with the CPU and memory on a board similar to an SBC, this machine has a fairly standard motherboard with an AMD 8088 derivative on the mobo, along with the memory; a bunch of jumpers on a daughterboard that holds the DB25 serial and XT keyboard socket (mounted in a slot so it looks like a regular Z-150 from the outside too), and a set of 8 DIP switches on the motherboard for.. I dunno. I've got it to boot from a floppy, and a flashfloppy, but if I put my XT-IDE card in, the machine just beeps once when the power is turned on, and that's all. This XT-IDE card worked fine on an Epson 8088 that died, hasn't been used since. I'd really love to find docs on this machine, to find out what the DIP switches do - maybe there's a port conflict with 300h. who knows? I'm going to have to find some bootable software that will scan the hardware and give me some ideas whats going on.

Reply 27732 of 27960, by Bruninho

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I received an Apple DuoDisk for my Apple IIe Platinum and I am in the process of inspecting the internals and also a cleanup before proceeding to some testing.

I think the DuoDisk also needs some retrobright...

"Design isn't just what it looks like and feels like. Design is how it works."
JOBS, Steve.
READ: Right to Repair sucks and is illegal!

Reply 27733 of 27960, by liqmat

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BigDave wrote on 2024-06-08, 18:23:

In the 80s I had a 16K RAM, but now I've got a Penultimate+ cart, so that does RAM upto 32/35k, but guessed more people these days would have either a regular switchable RAM pack, or Super Expander Cart since they're cheaper, which is also a 3K RAM pack, plus, old habits die hard!
OMG that Dev's work, WOW! it's amazing what can be squeezed out of the little VIC, I'm in total admiration of these real programmers. The Popeye game is fantastic, and was a favourite of mine in the arcades back in the day.

and then this happened in 2024. A very good Prince of Persia for the VIC-20. 35K of course.

https://youtu.be/_osxFXC_ZAY?si=jik58RAv9vUkeUIz

Reply 27734 of 27960, by NHVintage

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Holy cow, I thought when I bought a Zenith Z-150 Series PC this week I'd have no problem finding documentation for it, I find ZDS documents everywhere I turn... and boy was I wrong!

Upon arrival, I opened the case and was presented with... a standard CPU on the motherboard configuration! With a wrinkle - a daughterboard with the printer and XT keyboard port and a whole lotta jumpers (and no hint what they do even tho they had a ton of blank board to etch it on). One 8-switch DIP switch set on the motherboard, no labelling).

For those not familiar, Z-150 series usually have a backplane only in the chassis, with a CPU/memory card, and other cards. And thats the design all of the documentation I can find covers. No mention of this board configuration anywhere. And when I put in my XT-IDE card, all the computer does is beep, no video or other signs of life.

I spent hours researching with no joy. So I did what I usually do: go to bed and sleep on it. And this morning I remembered stason.org where I found what is apparently the only piece of information on this model ON THE ENTIRE INTERNET - it's a Z-157 Model2/3 . The model code for these starts with ZDH. But even this site doesn't tell me what all the jumpers on the daughterboard do, though I suspect the two next to the keyboard port are keyboard settings.
https://stason.org/TULARC/pc/motherboar ... EL-3.html

If anyone has more information on this model I'd love to get some, but as far as I can tell now all I can try is reprogramming the XT-IDE BIOS with a different address and see if that resolves the issue (and doesn't conflict with anything else).. which means putting the card in a different PC that'll boot with it installed so I can use the program to change the BIOS settings. Ah well. At least it works.

20240608_145155.jpg?ex=6666a2ab&is=6665512b&hm=85953166fd2d7ba4672dc990f5e464fef8145e492a86ea7fab72aaa7c4bd59ad&=&format=webp&width=883&height=662

Last edited by NHVintage on 2024-06-09, 15:30. Edited 1 time in total.

Reply 27735 of 27960, by PC@LIVE

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I had an ASUS CUV4X in my hands, which needed to be tested, with a P3 370 733MHz, after the first attempts didn't go well, I understood that there was a RAM problem, I tried different SDRAMs, and the third module I tried, solved it the problem, the PC started, it's alive!!!!!!!!!!
While waiting to gather more hw, I tried booting from DOS, and launched a couple of programs, diagnostics and bench.

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AMD 286-16 287-10 4MB HD 45MB VGA 256KB
AMD 386DX-40 Intel 387 8MB HD 81MB VGA 256KB
Cyrix 486DLC-40 IIT387-40 8MB VGA 512KB
AMD 5X86-133 16MB VGA VLB CL5428 2MB and many others
AMD K62+ 550 SOYO 5EMA+ and many others
AST Pentium Pro 200 MHz L2 256KB

Reply 27736 of 27960, by stef80

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Tested few mobile Bartons on Abit NF7-S with Corsair TCCD sticks:

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Reply 27737 of 27960, by Thermalwrong

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PC@LIVE wrote on 2024-06-09, 14:11:

I had an ASUS CUV4X in my hands, which needed to be tested, with a P3 370 733MHz, after the first attempts didn't go well, I understood that there was a RAM problem, I tried different SDRAMs, and the third module I tried, solved it the problem, the PC started, it's alive!!!!!!!!!!
While waiting to gather more hw, I tried booting from DOS, and launched a couple of programs, diagnostics and bench.

That heatsink seems like an odd one for a pentium III, is that maybe from some Socket 7 system?

I got hold of a Sony PRD-250 CD-ROM Discman player, which is a SCSI CD-ROM drive but is missing its cable and I've decided I like SCSI drives now. But it didn't read discs at all, just hunting around when trying to play pressed audio CDs.
Using a junky webcam, I confirmed that the laser was working and the focus system was working well, the carriage could move freely so it was probably a laser problem, like it's worn out.

I was getting nowhere and was going to give up then realised I have nothing to lose since they're not common drives and I had found the PRD-650 service manual which gave me some understanding of the TEST mode it could be put into by soldering together a solder jumper. I also learned that the laser assembly (DAX-02S) is probably irreplaceable.
I've never fixed a CD player before but I have two oscilloscopes, one is the Owon HDS2102S portable scope and the other is the Rigol DS1054Z - the latter gets used less because it is big and cumbersome in my opinion, but my view of it improved while trying to fix this drive. The control system is so much nicer than on a portable scope, and the screen is bigger.

So anyways, I took the player apart and started by taking pictures of everything - all the trimpots original positions and I tried marking them, this probably saved me.

IMG_3622 (Custom).JPG
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Because I hooked up the test points RFO (RF output?) to see the diamond pattern, VC as the ground point, TE for the E-F balance. Initially I tried using the Owon scope but I didn't know about its persistence settings so could not get anything resembling an 'eye' pattern that the service manual says to look for. Then settings were adjusted wildly for a while.

IMG_3624 (Custom).JPG
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I then switched to the Rigol scope, watched some videos of other people looking at this signal and started to understand what I was looking at. Soon after I could see something resembling the diamond type pattern but the voltage levels (vpp) were too low and it was noisy, so the laser did need boosting I think...?

Took off some capacitors to test whether those could be causing issues and no, they're not leaking and the ESR values were in spec for the 2 I tested.

Through the course of the night I adjusted everything, all the trimpots though only 3 mattered -
- The trimpot on the laser diode itself which of course the service manual didn't mention because that's set in the factory. It started off at something like 1.7v and I put it up to 1.71v or something - that was measuring on some test points by the laser diode so I'm pretty sure that's the voltage it's being fed?
- Then the Focus Bias adjustment which is the one that really made the difference, very finnicky adjustment
- The E-F Balance which seemed to set the high/low of the voltage and also made a difference to the eye pattern, in that the eye pattern only looked good once the E-F was set in the middle so the upper and lower waveforms matched and weren't clipping
There's also the Focus / Tracking gain adjustment pots but adjusting them did nothing positive so I pretty much have them back in their original positions which worked best.

I probably had the player functional last night since it was playing audio sometimes but broken up - that's going to happen in test mode because the carriage can be moved in/out using the |<< and >>| buttons, it's not playing an audio track, just a repeating bitstream.
Eventually I gave up thinking there was no hope and went to bed.

Got back to it in the morning and somehow I had the player reliably making sound in test mode, then playing audio and giving a nice 'diamond' / 'eye' pattern in something like 20 minutes of fiddling with it again.

prd-250-repair-eye-pattern.JPG
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From the above picture I realised the amplitude was now too high so put the laser voltage back down and the RFO test point now shows 1.2v vpp which is in spec I think. It's now adjusted just a little bit higher than its original setting.

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Reply 27738 of 27960, by PC@LIVE

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Thermalwrong wrote on 2024-06-09, 20:08:
That heatsink seems like an odd one for a pentium III, is that maybe from some Socket 7 system? […]
Show full quote
PC@LIVE wrote on 2024-06-09, 14:11:

I had an ASUS CUV4X in my hands, which needed to be tested, with a P3 370 733MHz, after the first attempts didn't go well, I understood that there was a RAM problem, I tried different SDRAMs, and the third module I tried, solved it the problem, the PC started, it's alive!!!!!!!!!!
While waiting to gather more hw, I tried booting from DOS, and launched a couple of programs, diagnostics and bench.

That heatsink seems like an odd one for a pentium III, is that maybe from some Socket 7 system?

I got hold of a Sony PRD-250 CD-ROM Discman player, which is a SCSI CD-ROM drive but is missing its cable and I've decided I like SCSI drives now. But it didn't read discs at all, just hunting around when trying to play pressed audio CDs.
Using a junky webcam, I confirmed that the laser was working and the focus system was working well, the carriage could move freely so it was probably a laser problem, like it's worn out.

I was getting nowhere and was going to give up then realised I have nothing to lose since they're not common drives and I had found the PRD-650 service manual which gave me some understanding of the TEST mode it could be put into by soldering together a solder jumper. I also learned that the laser assembly (DAX-02S) is probably irreplaceable.
I've never fixed a CD player before but I have two oscilloscopes, one is the Owon HDS2102S portable scope and the other is the Rigol DS1054Z - the latter gets used less because it is big and cumbersome in my opinion, but my view of it improved while trying to fix this drive. The control system is so much nicer than on a portable scope, and the screen is bigger.

So anyways, I took the player apart and started by taking pictures of everything - all the trimpots original positions and I tried marking them, this probably saved me.
IMG_3622 (Custom).JPG
Because I hooked up the test points RFO (RF output?) to see the diamond pattern, VC as the ground point, TE for the E-F balance. Initially I tried using the Owon scope but I didn't know about its persistence settings so could not get anything resembling an 'eye' pattern that the service manual says to look for. Then settings were adjusted wildly for a while.
IMG_3624 (Custom).JPG
I then switched to the Rigol scope, watched some videos of other people looking at this signal and started to understand what I was looking at. Soon after I could see something resembling the diamond type pattern but the voltage levels (vpp) were too low and it was noisy, so the laser did need boosting I think...?

Took off some capacitors to test whether those could be causing issues and no, they're not leaking and the ESR values were in spec for the 2 I tested.

Through the course of the night I adjusted everything, all the trimpots though only 3 mattered -
- The trimpot on the laser diode itself which of course the service manual didn't mention because that's set in the factory. It started off at something like 1.7v and I put it up to 1.71v or something - that was measuring on some test points by the laser diode so I'm pretty sure that's the voltage it's being fed?
- Then the Focus Bias adjustment which is the one that really made the difference, very finnicky adjustment
- The E-F Balance which seemed to set the high/low of the voltage and also made a difference to the eye pattern, in that the eye pattern only looked good once the E-F was set in the middle so the upper and lower waveforms matched and weren't clipping
There's also the Focus / Tracking gain adjustment pots but adjusting them did nothing positive so I pretty much have them back in their original positions which worked best.

I probably had the player functional last night since it was playing audio sometimes but broken up - that's going to happen in test mode because the carriage can be moved in/out using the |<< and >>| buttons, it's not playing an audio track, just a repeating bitstream.
Eventually I gave up thinking there was no hope and went to bed.

Got back to it in the morning and somehow I had the player reliably making sound in test mode, then playing audio and giving a nice 'diamond' / 'eye' pattern in something like 20 minutes of fiddling with it again.
prd-250-repair-eye-pattern.JPG
From the above picture I realised the amplitude was now too high so put the laser voltage back down and the RFO test point now shows 1.2v vpp which is in spec I think. It's now adjusted just a little bit higher than its original setting.
prd-250-repair-eye-pattern-2.JPG

Yes, it's not from a socket 370, it should be from an S7, perhaps coming from a Compaq PC, for temporary use anyway, that's fine, I'll put another one in when I've finished, and found the right mix between CPU RAM and cards, not I have decided nothing, but I think of increasing the RAM, putting a suitable AGP VGA, and if I wanted I could change the P3 with a more overclockable one, for example a 700, or I can simply change it with an 800-1000.

AMD 286-16 287-10 4MB HD 45MB VGA 256KB
AMD 386DX-40 Intel 387 8MB HD 81MB VGA 256KB
Cyrix 486DLC-40 IIT387-40 8MB VGA 512KB
AMD 5X86-133 16MB VGA VLB CL5428 2MB and many others
AMD K62+ 550 SOYO 5EMA+ and many others
AST Pentium Pro 200 MHz L2 256KB

Reply 27739 of 27960, by BitWrangler

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Thermalwrong wrote on 2024-06-09, 20:08:
That heatsink seems like an odd one for a pentium III, is that maybe from some Socket 7 system? […]
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PC@LIVE wrote on 2024-06-09, 14:11:

I had an ASUS CUV4X in my hands, which needed to be tested, with a P3 370 733MHz, after the first attempts didn't go well, I understood that there was a RAM problem, I tried different SDRAMs, and the third module I tried, solved it the problem, the PC started, it's alive!!!!!!!!!!
While waiting to gather more hw, I tried booting from DOS, and launched a couple of programs, diagnostics and bench.

That heatsink seems like an odd one for a pentium III, is that maybe from some Socket 7 system?

I got hold of a Sony PRD-250 CD-ROM Discman player, which is a SCSI CD-ROM drive but is missing its cable and I've decided I like SCSI drives now. But it didn't read discs at all, just hunting around when trying to play pressed audio CDs.
Using a junky webcam, I confirmed that the laser was working and the focus system was working well, the carriage could move freely so it was probably a laser problem, like it's worn out.

I was getting nowhere and was going to give up then realised I have nothing to lose since they're not common drives and I had found the PRD-650 service manual which gave me some understanding of the TEST mode it could be put into by soldering together a solder jumper. I also learned that the laser assembly (DAX-02S) is probably irreplaceable.
I've never fixed a CD player before but I have two oscilloscopes, one is the Owon HDS2102S portable scope and the other is the Rigol DS1054Z - the latter gets used less because it is big and cumbersome in my opinion, but my view of it improved while trying to fix this drive. The control system is so much nicer than on a portable scope, and the screen is bigger.

So anyways, I took the player apart and started by taking pictures of everything - all the trimpots original positions and I tried marking them, this probably saved me.
IMG_3622 (Custom).JPG
Because I hooked up the test points RFO (RF output?) to see the diamond pattern, VC as the ground point, TE for the E-F balance. Initially I tried using the Owon scope but I didn't know about its persistence settings so could not get anything resembling an 'eye' pattern that the service manual says to look for. Then settings were adjusted wildly for a while.
IMG_3624 (Custom).JPG
I then switched to the Rigol scope, watched some videos of other people looking at this signal and started to understand what I was looking at. Soon after I could see something resembling the diamond type pattern but the voltage levels (vpp) were too low and it was noisy, so the laser did need boosting I think...?

Took off some capacitors to test whether those could be causing issues and no, they're not leaking and the ESR values were in spec for the 2 I tested.

Through the course of the night I adjusted everything, all the trimpots though only 3 mattered -
- The trimpot on the laser diode itself which of course the service manual didn't mention because that's set in the factory. It started off at something like 1.7v and I put it up to 1.71v or something - that was measuring on some test points by the laser diode so I'm pretty sure that's the voltage it's being fed?
- Then the Focus Bias adjustment which is the one that really made the difference, very finnicky adjustment
- The E-F Balance which seemed to set the high/low of the voltage and also made a difference to the eye pattern, in that the eye pattern only looked good once the E-F was set in the middle so the upper and lower waveforms matched and weren't clipping
There's also the Focus / Tracking gain adjustment pots but adjusting them did nothing positive so I pretty much have them back in their original positions which worked best.

I probably had the player functional last night since it was playing audio sometimes but broken up - that's going to happen in test mode because the carriage can be moved in/out using the |<< and >>| buttons, it's not playing an audio track, just a repeating bitstream.
Eventually I gave up thinking there was no hope and went to bed.

Got back to it in the morning and somehow I had the player reliably making sound in test mode, then playing audio and giving a nice 'diamond' / 'eye' pattern in something like 20 minutes of fiddling with it again.
prd-250-repair-eye-pattern.JPG
From the above picture I realised the amplitude was now too high so put the laser voltage back down and the RFO test point now shows 1.2v vpp which is in spec I think. It's now adjusted just a little bit higher than its original setting.
prd-250-repair-eye-pattern-2.JPG

Hmmm my 1Mhz scope is suddenly sounding more useful.

Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.