Excellent video! I have a welding tip cleaner that works perfectly along with using Deox it in my tube sockets. Just find the correct diameter tip cleaner and cut the smooth end off w some nice dikes, and file it round.

I recently built a JMP 2203 superbass clone using a ST1 replacement board from Granger amps. Everything seems to be fine but one problem I keep having is that the power tubes red plate no matter what voltage the bias is set to. They heat up after like 10 seconds of the standby being turned on. The tubes are brand new EL34s by JJ. None of the screen resistors start excessively heat up either. I noticed though when turning the bias trim pot, I don't have very much of a range. It's a 22k piher, but it barely adjusts from -45 to -38 volts. Any clue what would cause this? I have a Marston 2562 PT and a Heyboer 100W OT

Looks like an old school diagnostic machine. Similar to what I used to test my amp tubes with in the 60s. Are these still the choice for diagnostics today, on yesterday's old school amps and technology??

@retrotechandelectronics

5 жыл бұрын

Its what I use, I cant speak for others.

I have been in search of a schematic or service manual for this version of the JCM800 with the PCB. Any ideas?

@jesse75

4 ай бұрын

Same. My amp also quit working.

original tubes and caps. then over fusing the HT. all recipes for expensive disaster.

Nice Video... Whats the name of the machine you using for testing the TUBE..? thanks

@retrotechandelectronics

3 жыл бұрын

I have a whole playlist dedicated to the restoration of that unit kzread.info/dash/bejne/q2Snl66qer25oso.html

My problem is so simple yet it's stumped me for 3 months.! Tried to get the right fuse caps for this 50 watt jcm 800 lead model 2205. An amplifiers place from England sent me something that's way too small. This amp isn't even broken. I just lost the fuse caps about 10 years ago...I turned acoustic for a while and basically ran away to my other skill of teaching karate... But now I need to make it work again. After contacting Marshall they said it was part number 00033 or 00037? I think it's pretty funny when Marshall doesn't even know. If you or some of the commenters could give me some clarity ! that would be awesome

Can replacing the filter caps be the issue of noisy amplifier as well?

@retrotechandelectronics

3 жыл бұрын

Yes, absolutely

I have a 2203 Marshall with a 1984 inspection date. I've owned it since around 1994. It probably has the original caps in it. When I look for cap kits for it, the suppliers list an early kit with 6 large caps and a later kit with 3 large caps. My amp actually has 5 large caps in it- 4 between the two large transformers and 1 in front of the preamp tubes. Is this an oddball amp? I guess I could just buy the 6 cap kit and not use one of them.

@scottdunn2178

3 жыл бұрын

Yes. This is the change I spoke of. They did it in order to cut corners and save money. Big mistake... those amps sound like dogshit compared to earlier 2203's.

@greglivo

3 жыл бұрын

@@scottdunn2178 It didn't sound great when I got it. I've modded it quite a bit and it sounds great now.

@scottdunn2178

3 жыл бұрын

@@greglivo Marshalls are a crap shoot, they either sound killer box stock... but most need a little tweaking > components have a +/- 20% tolerance, so you can mess with the values a bit... but some amps just don't have it no matter what. Regards 🎸

@greglivo

3 жыл бұрын

@@scottdunn2178 I bought it around 1994. I did the mods back then. I had a paperback spiral book about hot-rodding tube amps and did a lot of the stuff from that. I remember swapping out some resistors on the first gain stage and I think one capacitor. I also pulled the 4 6550 power tubes and replaced with 2 EL34 tubes to run it in 50 Watt mode. I got a schematic from somewhere for an effects loop mod that involved adding another preamp tube. The loop itself didn't work out very well. It sounds like the impedance is way off when I use it. It has no bass response at all. Fortunately, it woke up the sound when not using the effects loop and I'm happy with the final sound. These have become collectible so in hindsight I wish I hadn't drill another hole in the chassis for the tube. I did, however reuse one of the speaker outputs and the direct line out for my loop jacks so the back panel is still unmolested. Thanks for the info in your other comment about the European dating system. Never thought of that. It makes sense that it was built in November of '84. Probably one of the first horizontal jack ones made.

@scottdunn2178

3 жыл бұрын

@@greglivo I'm 54, and lived through the whole "hot-rod" era, when guys would spend hundreds or thousands modifying their Marshalls... and most of the time they discovered that their amp sounded just as good... if not better just using a $50 stomp box. And yeah, effects loops don't work in Marshalls... they are a complete tone suck... even "active" loops using an added tube. You're much better off using a good quality REACTIVE load box (never resistive), and tapping a line signal from that, running through your effects, then into a separate power amp. None of us ever thought we'd ever get old enough to see JCM 800's become "vintage" collectible! Ha! Good luck 👍

It was a nice video...a bit verbose...but nice. Any amp in this ilk,... all filter caps and tubes should be replaced and sockets cleaned and/or adjusted as Standard Procedure. Really no question. We also highly suggest a signal path electrolytic cap replacement while we're in there. 90% of the time, the problems are shotgunned away and the liability for the shop in terms of return warranty repairs is practically nilled. Just sayin. I still enjoyed the look at another JCM800

It doesn't turn on booster chanel light Marshall jcm 800 lead series 2210. What can I do?

@retrotechandelectronics

2 жыл бұрын

Trace through the schematic...

Replacing the filter capacitors in any amplifier over 10 years old is just good preventative mojo.

@retrotechandelectronics

4 жыл бұрын

When it’s my equipment I have the freedom to do as I see fit. This is generally not the case.

@Skoora

2 жыл бұрын

10 years would be way ahead of schedule unless you see a physical bulge, deformity or leakage. More like 25 years and even it’s not guaranteed that they’re no good. Have owned a few Marshall’s with FC’s that old and still rockin’.

@scottdunn2178

2 жыл бұрын

@@Skoora And Murphy's Law says it will fail right into the first song at a gig...

This is one of those crappy reissue 800's. No wonder it's been taking a shit. The original "vertical input" JCM 800's were made between 1981 and 1985, at which time they changed the power supply of the 100w 2203/1959 in an effort to save money... those post-'85 amps can easily be identified by the horizontal input jacks (Marshall never changed the 50w 2204/1987). Those post-85 amps sound granier, harsher, and aren't as loud as the earlier 2203/1959.

@greglivo

3 жыл бұрын

I have a U.S. issue horizontal jack 2203 with an inspection date of 7-11-84. Maybe the production changes weren't done by calendar year. It originally came with 6550 power tubes but I converted it to EL34's. This amp looks different internally than mine.

@scottdunn2178

3 жыл бұрын

@@greglivo In Europe they put the date first... then the month... so, yours would have been inspected and tagged in November... not July.