For RK50, you can look at Octopart here: https://octopart.com/rk50114a0001-alps-7850315. Otherwise, the TKD 4CP2500s are well thought of, and the 4CP601s aren't too far behind. Much cheaper.

As for board placement, I would guess those that place the board at the rear do so to keep them close to the input jacks (noise). This would normally require that the volume pot use a shaft extender and also be placed at the back. For raising the resistors, 2mm should be plenty.

Thanks Pars.

6 hours ago, Reima said:

I see some builds have the amp boards at the back of the chassis and others at the front. Is there any benefit (sonic or otherwise) to putting them at the front or back?

As a rule of thumb try and keep the transformer as far away from the amp boards as possible. Board placement depends a great deal on whether you’re building a two box or one box chassis. Implementing a two box with an an external psu you do have the luxury of having the amp boards at the back close to the inputs and like Pars mentioned you can then use a long shaft for the volume pot. Btw I’ve not had any had hum issues when using fully encapsulated transformers.

@johnwmclean thank you. I should have taken the hint from the DIY T2 where the volume pot etc. are at the back of the chassis. I will most likely go with an external psu.

I have completed the GRLV, have not tested it as yet,

 

Tested the two C2M devices I pulled out of the Carbon board last night on one of those cheap chinese device testers. One of them tested as an NPN, the other as a MOS FET. Another new one tested as a MOS FET as well, so guessing the one that thought it was an NPN was the bad one. Tossed it.

Good riddance

Hi all
maybe someone has a link to kgsshv carbon schematic
I try to find, but I find either broken links or fragments of the schematic or documents that are not downloadable here(

 a

Edited April 17, 20233 yr by Pars

i was going to be much less friendly.

the file you are looking for is where it should be.

yes it seems to be a problem with my browser
if i just click on the document it tries to load but nothing happens

but if i copy the link to the document and open it in a new tab - everything works

very strange behavior

and the links to gilmore.chem.northwestern.edu seem to be just outdated some of them are quite old, it looks like that hosting is just outdated

Edited April 17, 20233 yr by usa_love

PSU for both: Carbon and GG (Ground Grid). With delay board for tubes filaments. Compact 22AWG wires can handle 700v DC, double shielded.

Another idea of mounting those heat generators using the JST jumpers.

Be aware that the JST XH series is only rated for 250V AC/DC.

Yes, better would be something like the MATE-N-LOK series from TE, for 3-pin Mouser # 571-1-770873-0 and # 571-1721661 for the cable side.

 

On 10/31/2023 at 1:19 PM, audiostar said:

Yes, better would be something like the MATE-N-LOK series from TE, for 3-pin Mouser # 571-1-770873-0 and # 571-1721661 for the cable side.

 

 

Updated for 571-1-770873-0.

Marvelous!

Here the crimp sockets for the cable side connectors, Mouser # 571-770988-1

One of the big F&T 680uF/550V caps in my carbon PSU decided it wanted to pop mid-listen. Was the v1.7 split PSU boards, specifically the one with the LV supply (the cap closer to the LV section was the one that popped). Certainly left a big mess of electrolytic fluid to clean up all over the inside...

The other 680uF caps were also starting to bulge, so I replaced all four. It's concerning that all the 680uF caps would start doing that after roughly 9 years, especially when there was a period of about 2 years where the amp simply wasn't turned on at all. Could the amp's heat be accelerating this?

Anyway, the cap seems to have taken out some other parts in the -450V supply with it. Getting about -30V at the output and around the same at the drain & source of the DN2540. I can get other measurements later if needed. Anything else it might've taken out besides the 10M90S (Q1/Q7)?

Edited August 8, 20241 yr by s_r

GRHV does not fail gracefully... most or all of the active parts might need replacing.

Sören B posted a good guide for trouble shooting somewhere. 

Well I've tried replacing the C2M1000170D, 2x 10M90S, and the DN2540 & got similar behavior. Then I swapped out the LT1021, same story. Then I swapped out all of the sand save for the four STTH512FPs (since I apparently don't have any spares of those). Now it slowly climbs to about -200V & hovers there. Unless only swapping out some parts at a time killed the previous replacements, or unless it's just the STTH512FPs, not sure what else could be the cause of the issue.

Edited August 9, 20241 yr by s_r

did you check 2N3904 and 24V Zener ? they also could gone with faulty GRHV

2N3904 was also replaced. Doing a diode check the 24V zeners & the 1N4007s get the same measurements as the ones on the working +450V supply. Haven't diode-checked all four but two of the STTH512FPs measure the same as on the working supply as well.

Edited August 9, 20241 yr by s_r

It must've been either the STTH512Ps or the 24V zeners (or both), since I replaced those and now I'm getting -461V at output. Likely replaced more than what was necessary but whatever, peace of mind is worth more than the parts cost.

Should be able to zip everything up and have this carbon playing music again tonight.

Congratulations! I have the same problem with my carbon. Both of the big capacitors in the negative supply died. It happened a few months ago but I can not persuade myself to start the repair until now. As I checked it again I see one of the capacitor in the positive supply is bulging too. These are from the first group buy I think. Where are yours from? So the advice is replace all the sands (and check the passives in between) the less time consuming?

;

1 hour ago, judo said:

Congratulations! I have the same problem with my carbon. Both of the big capacitors in the negative supply died. It happened a few months ago but I can not persuade myself to start the repair until now. As I checked it again I see one of the capacitor in the positive supply is bulging too. These are from the first group buy I think. Where are yours from? So the advice is replace all the sands (and check the passives in between) the less time consuming?

;

The caps were from the F&T cap group buy here years ago. Definitely going to be keeping a closer eye in the coming years for signs of them starting to bulge again. Like I mentioned earlier it's worrying that they would act this way after only so many years... One would expect caps to last at least a few decades of normal usage.

I probably replaced more of the sand than necessary, but the 24V zeners should likely be replaced too as ang728 mentioned.