Collection of mods for Beresford TC-7520

[MartinT]

I was going to suggest that you look at the ribbon cables but you've got there first. It shouldn't be too difficult to replace them with individual solid core wires if need be.

[fmzip]

Would stranded 24 gauge be OK?

[MartinT]

Would stranded 24 gauge be OK?

Hmm, the Americans remain ever imperial in their measurements! I don't know what that is but would be tempted to get hold of some solid core as it is so much easier to solder to a PCB.

[fmzip]

24 "gauge" lol......

I still don't know my metric conversions yet!

Good news, switching problem is resolved!

Bad news, I have no audio out of the right channel. Swapped op amps, same issue. Pressing on EC7 and EC9 brings the audio back. Replacing with new caps into those two locations, same result. Replaced both Wima caps, same issue.

I cooked something, the DAC chip get very hot very fast. Schematics please, I am begging.

I'm so bummed out. Final steps, the very last mod, and now its dead.

[HighFidelityGuy]

24 "gauge" lol......

I still don't know my metric conversions yet!

Good news, switching problem is resolved!

Bad news, I have no audio out of the right channel. Swapped op amps, same issue. Pressing on EC7 and EC9 brings the audio back. Replacing with new caps into those two locations, same result. Replaced both Wima caps, same issue.

I cooked something, the DAC chip get very hot very fast. Schematics please, I am begging.

I'm so bummed out. Final steps, the very last mod, and now its dead.

I don't beleave stan has officially made any schematics available and I doubt he'd like people posting them unofficially.

If the DAC chip is getting hot during normal use then it sounds like you've shorted something. The first place I'd check would be TC2 and C2 just to the right of the DAC chip. As the new TC2 replacement is bigger than the one it replaced it can get very close to C2. Make sure they're not shorting on each other. Also make sure all the new polarised electrolytic caps are installed with the correct polarity. Look for the tiny + symbols on the PCB and make sure the verticle white stripe on the new caps is on the oposite side. If you manage to find a wiring fault then you may have cooked the DAC chip, so you may have the replace that as well.

Also make sure you have the power regs the right way round. The white sticker should be facing the rear of the chassis. Also make sure you don't have any blobs of solder kicking around the board. Those beggers get everywhere during de-soldering.

I hope that helps.

[HighFidelityGuy]

Another place to check is EC15 and EC16. They're under the opamp board. Make sure the bottom of the opamp board isn't shorting on the top of these caps. A little insulating tape will do the trick. It's a good idea to do this anyway although I beleave later revisions have shorter caps.

[fmzip]

Thanks for all the suggestions.

Stan did reply indicating that the schematics are proprietary which was disappointing but understandable. I was under the assumption that this information was available with all the modding going on. I probably should have asked this question before I started modifying it. It is quite interesting how some companies hold everything close to the vest and others do not. For example about a month ago I requested a schematic from Rotel, and they sent me one after I provided them my serial number. With most of the electronics on the market, there really is nothing secretive inside of them.

I spent about 7 hours checking everything out. The new regulators are installed correctly as it worked for a period of time. The polarity of the caps are also correct.

Interesting point regarding the tape. I removed that in order to try to get the cover back on. The cover has been off since the beginning as it will still not fit with the Nichicon Muse caps installed on the op amp board. I believe the caps you are referring to "TC2 " just to the right of the DAC chip may have hit the leads of the DAC. Or, my ribbon cable breaking may have caused the short elsewhere.....

I am going to order a Caiman from Stan and he said he would sell me a new board as well for my TC-7520. What I will likely do is start all over with the TC-7520 mods and leave the Caiman as is. This way I will never be at a loss for sound

[MartinT]

The cover has been off since the beginning as it will still not fit with the Nichicon Muse caps installed on the op amp board.

Puzzling. Mine fit ok, certainly without fouling the lid. Are yours the green MUSE caps or another type?

[fmzip]

green ones.......they are a smidgen too tall

[fmzip]

Leo, could you please tell me the value of the 1/2W resistor directly behind RCA1 please.

If you could, I will be able to have some music once again!

Thanks