kosmonautmayhem wrote: ↑
Thu May 23, 2019 9:41 am
Oooh ! You're in it. Take some pics!
The lighting in my dining room sucks, but I took a few along the way. I discovered one thing which I have no explanation for... the 56k just before the speaker jack.. I measured it at 1.5k-1.6k double checking it with a second meter. I replaced it with a fresh one, fitted it up, everything sounds right, but I was back in there to adjust the bias again, so I rechecked the NEW one... 1.5k... I rechecked the old one now that it is out of the amp... 58k... I am sure there is some explanation but I just don't get it.
At any rate, I used a 24k in the bias circuit to get it back up and running. It sounded great but I had a tremolo issue (there's the tip off, right??) where I had this weird almost overtone like thing going on a little lower in volume than the actual signal. So I checked the bias, and these tubes are WAY mismatched! One was idling at about 19ma, the other about 11. I tried an 18k (which measured 18.5k) in there and it was much better but still a little off as evidenced by the term being a little weak at the top of the dial. At this point I'm reading about 22.4 on tube and 31(!) on the other. Not wanting to waste too much more time with these shitty tubes (because I already have a nice NOS pair of Raytheons on the way), I laid a 1k in series with the 18.5k and now the trem is better still and I'm idling at 20.1 and 28.6. These numbers were actually even worse with the sockets swapped. As soon as the new Raytheons get here, I'll be in business!
The amp is really quiet now, even up full. It is WAY more dynamic and touch sensitive. It was a bit stiff and flat before. It now has a better range of overdrive from none until about 5, then you gradually get more until the mini Marshall tones kick in about 9-10. I liked the way it sounded before. I
It was a bunch of work cleaning all the shitty ass work up. It had one 150uF cap SILICONED to the chassis instead of the 3 way can
And the AFTER!
Removed the death cap, kept the ground switch for aesthetics, and the grounded cord I went with is GRAY! I ground down and reused the old strain relief so that I didn't have to enlarge the hole in the chassis.
The whole thing. Right back to stock. I noticed afterward that there is an extra ground on the topside of the board that his since been removed.
AT this point I don't think it's too apparent that anything was ever done, except for the new cloth wire on 2 of the legs of the cap can.
Couple markings inside the cabinet: