VOGONS


First post, by appiah4

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I have been donated a Roland RAP-10. The part was given to along with the information that it does not work.

Apparently, it has had some extensive leaking capacitor problem and the previous owner had it recapped by an electronic service. The service has not done what I would call a commendable job with the recap, and appears to have lifted at least one trace which they shoddily bodged, but as far as I can test all the other capacitors have continuity from their terminals to the intended connections. The card was covered with flux but I did my best to clean that off with IPA.

The issue? It just doesn't work.

I am trying to get it working in a Socke 370 motherboard with a Celeron 333. It is jumpered for IRQ9 and Port330. I do not get any sound from it, when playing GM music, or when I try to get it detected in games that support it directly such as Abuse.

I get absolutely nothing out of the Line Out port, not even the slightest hiss or static. It's almost as if the card does not seem to get any power at all.

From what I can gather, it works on 5V from the ISA port alone, and the 5V on the card does not appear shorted.

I would really love to get this card working for my collection, but I don't know where to look and what to do. I have a multimeter and an oscilloscope. I am handy with a soldering iron. I am eager to get started 😀

Attached are photos of the card.. Help me VOGONS, you are my only hope.

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Reply 2 of 22, by Shponglefan

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When you say you've tested in games, does this include games that support it as a digital audio card (e.g. not just MIDI)?

If it's not being detected at all, then I'd start by testing traces and voltages from the ISA contacts, as well as testing for any loose pins on the ICs.

If you can look up pinouts on the various ICs, you can also test those for voltages to see if things are being sent/received.

There are a pile of Roland service manuals available here: http://www.synfo.nl/pages/servicemanuals.html

Unfortunately they don't have the RAP-10. However, it's possible that other synths from that era might have the same ICs, so you could potentially figure out some of the pinouts that way.

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Reply 3 of 22, by appiah4

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Yes, games that use it for digital audio do not detect its presence either.

I will start out by reflowing the legs of the ICs and report back then!

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Reply 4 of 22, by zuldan

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appiah4 wrote on 2024-05-04, 06:57:

Yes, games that use it for digital audio do not detect its presence either.

I will start out by reflowing the legs of the ICs and report back then!

Let us know how you go. I’m going to do the same with a SCB-55 that’s not working.

Reply 5 of 22, by Jackhead

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I would start removing all the caps and and cleaning. Maybe there is a short under a cap? Pads gone or something else. Good luck!

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Reply 6 of 22, by Thermalwrong

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There's evidence of corrosion in a few spots near to where the caps have leaked. Look at IC8 M51132L, I assume that's an amplifier or something? The solder joints don't look good and specifically the trace by the letter C of IC8
Similar thing with some of the pins / traces on IC3 as well, that doesn't look like flux.

IC2 looks like it's been removed at some point and isn't soldered down well on all pins.

Maybe it's the angle but the traces around IC41 where they branch down by the grid pattern solder-mask, those don't look great either. The traces around the CU41B capacitor look damaged.

If you've got an oscilloscope, check that the crystals. I found a Yamaha OPL3-SAx soundcard that was working on the digital side but couldn't make audio because the 33mhz crystal was broken.

I guess that you've got it able to detect in Windows but there's no sound? I would suspect -5v line but there's no trace for that on the ISA connector so that's not the issue. Could the card be speed sensitive?
Try different IRQ / IO settings to make sure it's not just a device conflict.
Check what it does in Windows with the RAP-10 driver / audio tools since that looks like it should be useful for diagnosing where the problem lies.

Reply 7 of 22, by beeper6581

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If you have a steady hand you can try probing around the DAC (IC12) when you have something that is playing music through it on the PC. There should be a digital supply and clock and data going in, and an analogue supply and audio coming out somewhere.

Reply 8 of 22, by appiah4

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Thanks to all the suggestions, I will start looking into all the replies VERY SOON. But in the meantime, here is a twist:

When I set the Switch 1 to ON, MSD actually recognizes a gameport attached to the computer, so the card does get power and work to some extent!

Moreover, now that I attached an amplified speaker to the OUT port instead of a hifi headphone, I can actually hear a very, very, very low and VERY distorted and muffled music playing when I run DOOM and the Music is set to GM so I gues the Synthesis IS working, but maybe the dac or the amplification is not?

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Reply 9 of 22, by Shponglefan

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appiah4 wrote on 2024-05-05, 14:05:

Moreover, now that I attached an amplified speaker to the OUT port instead of a hifi headphone, I can actually hear a very, very, very low and VERY distorted and muffled music playing when I run DOOM and the Music is set to GM so I gues the Synthesis IS working, but maybe the dac or the amplification is not?

That's positive news. That suggests that all the main sound generation components should be working.

I'd start by checking the DAC in this case. As beeper6581 suggested, you can probe the inputs and outputs of the DAC to see what sort of signal you are getting.

This could be as simple as just bad caps on the audio circuit.

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Reply 10 of 22, by appiah4

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Shponglefan wrote on 2024-05-05, 15:24:
That's positive news. That suggests that all the main sound generation components should be working. […]
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appiah4 wrote on 2024-05-05, 14:05:

Moreover, now that I attached an amplified speaker to the OUT port instead of a hifi headphone, I can actually hear a very, very, very low and VERY distorted and muffled music playing when I run DOOM and the Music is set to GM so I gues the Synthesis IS working, but maybe the dac or the amplification is not?

That's positive news. That suggests that all the main sound generation components should be working.

I'd start by checking the DAC in this case. As beeper6581 suggested, you can probe the inputs and outputs of the DAC to see what sort of signal you are getting.

This could be as simple as just bad caps on the audio circuit.

Yes, LC7886M (IC6) I believe is the DAC that needs to be checked. It has a dodgy looking pin on the upper left that may not be soldered down properly. I'll check all its connections.

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Reply 11 of 22, by appiah4

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Well, some updates. I've reflowed all the legs of IC6 (LC7886M) which I thought was the DAC, but that did not resolve the issue. In the process I noticed that CU6A actually had a cold solder on the side attached to the ground plane and was floating. I soldered that back down.. and no, that did not fix the issue either. But that did show the how bad the recap job on this card is, so I wouldn't be surprised to find out more soldering issues.

In other news, I actually looked up LC7886M and it's not actually a DAC but an ADC so that is probably responsible for handling Line In and/or Aux, so I was reflowing the wrong IC. Fantastic. The DAC is actually a D6376 at IC12. I will reflow that IC, then check any nearby caps for bad solderjobs. Then I'll check its voltage pins to see what it's getting, and I'll probe with a scope to see if it has a good CLK input, and what activity there is on the input and output pins..

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Reply 12 of 22, by Tiido

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Since there was some sound the problem is going to lie in the sea of capacitors and 8 pin chips (the analog area). It is possible some passives don't connect, and perhaps cause something like a missing reference voltage or a power rail...
EDIT: other option is that vinegar bath was not done and there's some conductive stuff left somewhere under the chips and causing problems. In general you should be able to follow the sound path from DAC through each chip + any capacitors on the path and eventually find a chip where sound is not passing through anymore.

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Reply 13 of 22, by appiah4

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Well, I have reflowed the DAC and then all the electrolytic SMD capacitors in the area, but that did not help. That leaves me thinking maybe one of the untouched but oxidized smd capacitors in the vicinity is the problem, so I will reflow all of those later this week. I haven't put the oscilloscope to use yet, but I did get voltage readings on all the pins of the DAC. I don't have them with me right now, but I'll post them later today.

As I mentioned earlier, I can hear SOMETHING in both channels when I play MIDI to the card, however it is not music. It is basically a nearly inaudible static/crackling, but in rythm with the music (I know Doom E1M1 by heart 😁) so maybe, possibly, the issue is not with the amplification but with the synthesis in general? Particularly considering Abuse (DOS game with support for RAP-10 digital sound) can also not play to the card and can not detect it (hangs at detection).

This will all hopefully be much easier when I start probing around with the scope..

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Reply 15 of 22, by appiah4

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Tempus wrote on 2024-05-07, 09:32:

Does the RAP-10 require -5V? I am prettty sure I’ve used mine without.

There is no contact on the edge connector for -5V so I'm almost certain it does not make use of -5V. It only gets 5V from the ISA bus from 3 different contacts.

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Reply 16 of 22, by appiah4

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OK so I have my notes and here are the voltages I found on the pins of (what I think is) the DAC :

DAC D6376

Pin 1: 4/8 SEL 0V
Pin 2: D.GND 0V
Pin 3: NC 0V
Pin 4: D.VDD 4.75V
Pin 5: A.GND 0
Pin 6: R.OUT 1.57V
Pin 7: A.VDD 4.99V
Pin 8: A.VDD.99V
Pin 9: R.REF 2.17V
Pin 10: L.REF 2.17V
Pin 11: L.OUT 1.58V
Pin 12: A.GND 0
Pin 13: L.RCK 1.39V
Pin 14: LR.SEL 4.75V
Pin 15: S1 0V
Pin 16: CLK 1.49V

This is with Doom playing MIDI music at 50% volume.

D.VDD is 4.75V and in spec (4.5-5.5V), the digital block is getting power.
A.VDD is 5.00V and in spec (4.5-5.5V), the analog block is getting power.
L/R.REF are connected to ground through a capacitor each, as the datasheed suggests, and seem to be fine at 2.17V - although what these are used for I can not say.
VOUT should be VDD+0.3 max, which would be 5.0, so at 50% volume I'd expect around 2.5V on the L/R.OUT. There is only 1.57/1.58V on them. Considering this is probably a waveform I am seeing less than its max, so I'd guess that is fine.

Is there anything I am missing? It looks like the DAC is doing what it should?

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Reply 17 of 22, by Shponglefan

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appiah4 wrote on 2024-05-07, 10:29:

Is there anything I am missing? It looks like the DAC is doing what it should?

To really test this, you can check with the oscilloscope. The input pin(s) should have a data signal flowing in. The output pins should have something that looks like an analog sound wave.

I posted some oscilloscope examples in my own thread on diagnosing a faulty Roland SCC-1: Faulty Roland SCC-1 (no audio): attempts to diagnose and repair this card

I would also suggest testing the digital audio portion with other games and even in another system if possible. You want to rule out the possibility of a driver/software/system issue, if the card isn't being detected.

It's possible the card has multiple faults. But the fact that you're getting some sort of output when MIDI is playing, that's a positive sign at least.

Last edited by Shponglefan on 2024-05-07, 14:39. Edited 1 time in total.

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