Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: CrimsonGhost on February 02, 2025, 04:14:52 pm

Title: Sound City Concord Advice
Post by: CrimsonGhost on February 02, 2025, 04:14:52 pm

Hello everyone,

I have a Sound City Concord amplifier that I was checking over and I noticed there are two capacitors that have much higher voltages passing over them than they are rated to. The capacitors appear to be original and it doesn't look like anyone has ever tampered with it.

The capacitors are both 4uf 50vdc, both CCL branded

Im surprised these have survived?

Title: Re: Sound City Concord Advice
Post by: shooter on February 02, 2025, 04:52:28 pm

seems somethings missing, ain't got time to hunt, here's the link for the schematic, PG 4 is Concord
find them on the schematic, then maybe I'll be able to help more


https://el34world.com/charts/Schematics/files/Soundcity/Sound_city_amps.pdf

Title: Re: Sound City Concord Advice
Post by: CrimsonGhost on February 02, 2025, 05:37:53 pm

Interesting, Ive never seen that schematic before. I have a home brew one that I found on Google. The schematic I have has those capacitors down as 4.7uf 350v, that was what prompted me to check them.

I think Ive identified them on the schematic you provided, Ive also included a picture of the schematic I have for comparison, although its very different visually, it seems to line up with what I have in my amp anyway.

Im still a novice though so any extra input would help....

Title: Re: Sound City Concord Advice
Post by: Latole on February 03, 2025, 04:40:30 am

What is the wall outlet voltage where you living ? 240 vac, 120 vac. ...... ?

A higher input voltage than originally intended for the amp causes a higher B+ voltage.

Title: Re: Sound City Concord Advice
Post by: CrimsonGhost on February 03, 2025, 05:12:56 am

The power in my house is 245v and the selector at the back of the amp is also in the 245v position.

I believe the amp is entirely original, I cant see anything that looks new and all the solder joints look uniform with each other so I don't think it has been tampered with?

Here's a full layout inside the amp.


Edit: The only thing I did notice was my VU meter wasn't working on the amp, looking inside I can see the little trim pot is turned all the way off, its beside the output valve on the left hand side, it might mean someone has been in the amp but it also may have been a Sound City employee who simply forgot to move the trim pot in to the correct position? I have no idea.

Title: Re: Sound City Concord Advice
Post by: jojokeo on February 03, 2025, 06:46:15 pm

ChrimsonGhost - Off topic but wanted to ask, did you ever keep a reef aquarium and hobby?