VOGONS


Options for a bad oscillator?

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First post, by yourepicfailure

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Hoping this is appropriate for this board. I guess according to the TOU, it says "electronic hardware and software" with no delimitation, so I guess it fits here.

Hoping to get some input here, I have a piece of equipment (a camera) that is fairly borked. After a long time of troubleshooting, I have identified a bad VCO as the culprit.
Redid the soldering to make sure, and currently the only way to "get it working" temporarily is to tap it a couple of times.
This is the oscillator:

oscillator.png
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And where it lives in the schematic:

tg-32schematic.png
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Sadly, I can't seem to find anything on this oscillator except an OEM part number. I also can't affordably source a "for parts" unit for a replacement.
As for other specs I can derive, it is powered by 5 Volts.
What are some options here that I can take to either try and fix it or replace it? Due to its really really embedded position, repeatedly "tapping it" is not a viable long-term solution.

Reply 3 of 22, by quigonhu

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Well, first you have to be sure the oscillator is defective.
Then try to double check the VCC.

Regarding the electronic components purchasing, we don't consider ebay, amazon etc... normally I contact the original factory or the agents. For small order, I prefer mouser, rsonline, digikey and element14. Mouser would be my first choise btw.

Reply 4 of 22, by Tiido

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majestyk wrote on 2024-05-28, 04:16:

The PCB layout also allows for larger oscillators - like this one
https://www.ebay.com/itm/256258430278?

This will not do, as it is a bare oscillator with fixed frequency. What is needed is a VCO because there's need to tune the oscillation frequency. VCO aspect comes into play to align things with whatever the incoming reference is.

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Reply 5 of 22, by myne

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https://www.mouser.com/c/passive-components/f … cy=28.636%20MHz

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Reply 6 of 22, by Tiido

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And those are also just oscillators without way to tune the freq. I looked a bit in mouser and they don't carry anything suitable for this purpose, not the correct freq nor anything in stock.

T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
Newly made 4MB 60ns 30pin SIMMs ~
mida sa loed ? nagunii aru ei saa 😜

Reply 7 of 22, by myne

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Huh?
The original is 28.636mhz.
The link is filtered by 28.636mhz.

Why are you on about tuning? It's a simple case of finding the correct formfactor and swapping it.

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Reply 8 of 22, by Tiido

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Look at the schematic posted, the part is a VCO and not a regular oscillator. The freq tuning input is absolutely in use there and the device is most probably not going to work properly without that ability.

T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
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Reply 9 of 22, by myne

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Looks like it only chooses between pal and ntsc so wouldn't it make sense that they just dropped in a fixed oscillator like in the original image depending on the market?

Ie the variable is just"which market is this for? "

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Reply 10 of 22, by yourepicfailure

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Okay, to answer the first one
There is a specific mhz crystal installed for the region, in my case I have NTSC-U 28.6.
The voltage control is used by the camera to skew the clock to synchronize it to gen-lock and correct other skew. Not to select the frequency.
As for the second, I confirmed it's defective because if I give it a gentle tap it starts working for a few minutes. Also checked the solder job.

Reply 11 of 22, by myne

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Cool. See link to mouser above.
Find formfactor.
Get part no.
Find suitable supplier (if mouser doesn't deliver to you)
Order.

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Reply 13 of 22, by myne

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How many pins are under yours?
I looked on digikey and the vcos all look like more than 4 pins
Also, yours is clearly labelled with 28.636mhz.
That doesn't read like a variable thing.

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Reply 14 of 22, by Tiido

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it is a VCXO rather than just a VCO, which have much broader freq range. VCXO have a control voltage input that allows the freq to be tuned slightly, in the order of 0.1% or so because you cannot pull the crystal's freq very much due to very high Q they got. The control voltage range is also another concern about compatibility not just the freq itself but I imagine this is part of a PLL so this shouldn't be a too big of an obstancle.

Does that service manual have a parts list in addition to schematics ? It could yield some more info about what exactly is supposed to be in the place but it does seem like there will not be any directly compatible parts to be found very easily, I have not found anything even from chinese sources...

Closest is this : https://www.digikey.no/en/products/detail/ren … 636300I/2153957
But it isn't stocked and it is 3.3V. All other things I have been able to find part numbers of have been 3.3V too.

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Reply 15 of 22, by rasz_pl

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VCXO. You are looking for something like FAR-M2DB-27M636-F100, SaRonix is another manufacturer making those. Problem is its a 20 year old part (seen here for example in app note from renesas https://www.renesas.com/us/en/document/oth/tb … r-horiz-genlock) and EE moved on rapidly. While VXCO is easy to find and plenty to pick from, almost all will be 3.3V or less.

Tiido wrote on 2024-05-29, 13:58:

not a VCXO

Last edited by rasz_pl on 2024-05-29, 15:07. Edited 2 times in total.

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Reply 16 of 22, by Tiido

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It is in a VCXO category, and I went through the part number and the datasheet and it is a VCXO according to it also... But yes, 3.3V and not directly usable.

T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
Newly made 4MB 60ns 30pin SIMMs ~
mida sa loed ? nagunii aru ei saa 😜

Reply 18 of 22, by yourepicfailure

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Tiido wrote on 2024-05-29, 13:58:

Does that service manual have a parts list in addition to schematics ? It could yield some more info about what exactly is supposed to be in the place but it does seem like there will not be any directly compatible parts to be found very easily, I have not found anything even from chinese sources...

Unfortunately, the service manual only lists a Sony part #. Right now all I have is the readily available PAL manual, waiting for the seller to ship the NTSC flavor I ordered since the PAL only lists the PAL crystal.

rasz_pl wrote on 2024-05-29, 14:14:
VCXO. You are looking for something like FAR-M2DB-27M636-F100, SaRonix is another manufacturer making those. Problem is its a 20 […]
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VCXO. You are looking for something like FAR-M2DB-27M636-F100, SaRonix is another manufacturer making those. Problem is its a 20 year old part (seen here for example in app note from renesas https://www.renesas.com/us/en/document/oth/tb … r-horiz-genlock) and EE moved on rapidly. While VXCO is easy to find and plenty to pick from, almost all will be 3.3V or less.

Tiido wrote on 2024-05-29, 13:58:

not a VCXO

Thank you, these are a good start. In theory, there is enough real estate to toss in a small 3.3 reg. I did measure and that the crystal's peak output is 3.3v, so I might be able to get away with that.

I'll be waiting for the NTSC service manual to arrive, and if the Sony part number is unavailable, then I'll look into these alternates.

Reply 19 of 22, by kingcake

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myne wrote on 2024-05-28, 14:21:
Huh? The original is 28.636mhz. The link is filtered by 28.636mhz. […]
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Huh?
The original is 28.636mhz.
The link is filtered by 28.636mhz.

Why are you on about tuning? It's a simple case of finding the correct formfactor and swapping it.

It's not even close to that simple. There are oscillator modules and then there are bare crystals. Even if it was just a crystal, there are different types of crystals that are not interchangeable. Is it parallel resonant? Is it series resonant? If it's parallel resonant, what is it's ESR and what load capacitance does it require?

I know you've seen youtubers insert random unknown crystals on motherboards to overclock them, but you can't do that and expect good results.