Those switching jacks on Marshall's are notorious for not making good contact either causing intermittent preamp in and out issues. They seem to be the curse of modern amps. I check those first on about every amp I repair that has some kind of cutting out issues. yeah, this amp had much deeper issues, I haven't seen can caps that bulged ever. Nice job on the repair. I rebuild a lot of tube amps and the Marshall's are a SOB to get the chassis back in the cabinet at times.
God Dam i wish you were in toronto i need my jcm800 50 watt lead series combo amp fixed. its from 1986 and i bought it and it worked and then blew fuses and a larger tube ,bought a new tube and fuses and NADA. So its kinda looking like the amp you fixed. The guy i bought it from said it was sitting in his basement for years. Well thanks for the amazing video you and the guitologist are the only guys on youtube that are honest in your work and are very knowledgeable with every facet in guitar amp repair. Keep up the great work Bro and thanks.
The typical working-lifespan of an electrolytic cap, especially ones made using older technology, is reckoned to be about 10 or 20 years before they fail.
Any amp older than 20 years is ripe for recapping. You just need good eyes and no oscilloscope or other fancy stuff are needed. If you love your amp, replaced all electolytics at least every 15 years or so and you'll be good to go. Nowadays, electronic components are getting better and better... so, it always worth the job!
Caps are rated for a certain number of hours of use at full load, not so much shelf life. An amp that sits in a closet will be different than one that is gigged out daily.
One of the best ways to test an electrolytic capacitor, is to do something called an ESR test on it, ESR is short for Equivalent Series Resistance, and can be thought of as being like a virtual resistor in series with the capacitor, especially to AC, normally the ESR of an electrolytic capacitor should be very low which is important when it comes to power supply filtering, a bad electrolytic cap will show a higher ESR value than it normally should.
Biased a bit cold for a crunch monster. Around 42 is near perfect. In that ballpark. I didn't see you dissipate the voltage. It should be part of every service video.
I don't bother buying cheap tubes that Tube Depot says are matched. It's a fallacy. Secondly, you're biasing too cold for an amp that people expect crunch out of right out of the gate. I could maybe see being that conservative if you were using Mullards or Amperex in an effort to save them, but JJ's are cheap, so hotter isn't a bad thing. Thirdly, may I respectfully suggest that you lose the ring, especially since you're using your left hand in a high volt live amp. Sends the wrong message.
Read The Trainwreck Pages by legendary amp guru Ken Fischer, the section on bias adjustment... the safe operational range of EL34 etc. is between 10-40mA per tube... and all amps are different, some may sound better running colder, some sound better with more current at idle. Using Ken's preferred current method... "any current that produces the tone you desire is the "correct" setting". Regards 🎸
Those switching jacks on Marshall's are notorious for not making good contact either causing intermittent preamp in and out issues. They seem to be the curse of modern amps. I check those first on about every amp I repair that has some kind of cutting out issues. yeah, this amp had much deeper issues, I haven't seen can caps that bulged ever. Nice job on the repair. I rebuild a lot of tube amps and the Marshall's are a SOB to get the chassis back in the cabinet at times.
God Dam i wish you were in toronto i need my jcm800 50 watt lead series combo amp fixed. its from 1986 and i bought it and it worked and then blew fuses and a larger tube ,bought a new tube and fuses and NADA. So its kinda looking like the amp you fixed. The guy i bought it from said it was sitting in his basement for years. Well thanks for the amazing video you and the guitologist are the only guys on youtube that are honest in your work and are very knowledgeable with every facet in guitar amp repair. Keep up the great work Bro and thanks.
Its generally never a good idea to ply and pray a tube amp thats been sitting for years without close inspection.
Nice videos sir! Thank you for your service. I've got a JCM 800 Combo on the bench now and I think you've inspired me to make a video too!
Glad to hear it.
6:02 - This is when I prefer an analog meter - the pot-sweep test :)
Heathkit VTVM
Really liked your video !,.................,subscribed !
Thanks kindly!
The typical working-lifespan of an electrolytic cap, especially ones made using older technology, is reckoned to be about 10 or 20 years before they fail.
Any amp older than 20 years is ripe for recapping. You just need good eyes and no oscilloscope or other fancy stuff are needed. If you love your amp, replaced all electolytics at least every 15 years or so and you'll be good to go. Nowadays, electronic components are getting better and better... so, it always worth the job!
Caps are rated for a certain number of hours of use at full load, not so much shelf life. An amp that sits in a closet will be different than one that is gigged out daily.
In need of a schematic or service manual for this version with the PCB. Any leads? Thanks!
One of the best ways to test an electrolytic capacitor, is to do something called an ESR test on it, ESR is short for Equivalent Series Resistance, and can be thought of as being like a virtual resistor in series with the capacitor, especially to AC, normally the ESR of an electrolytic capacitor should be very low which is important when it comes to power supply filtering, a bad electrolytic cap will show a higher ESR value than it normally should.
You should check my videos where I go through all of these with an ESR meter. I have a few videos where I do the Power factor by hand.
More amp repair videos please.
Amp videos take a lot of time to make, not enough viewers....
Isn´t the JJE34L a 30W tube?
MAX 25w
Biased a bit cold for a crunch monster. Around 42 is near perfect. In that ballpark. I didn't see you dissipate the voltage. It should be part of every service video.
You're right. That will be the video where some guy decides to test the filter caps with their tongue.
@@retrotechandelectronics People are capable of much dumber things.
I don't bother buying cheap tubes that Tube Depot says are matched. It's a fallacy.
Secondly, you're biasing too cold for an amp that people expect crunch out of right out of the gate. I could maybe see being that conservative if you were using Mullards or Amperex in an effort to save them, but JJ's are cheap, so hotter isn't a bad thing. Thirdly, may I respectfully suggest that you lose the ring, especially since you're using your left hand in a high volt live amp. Sends the wrong message.
Read The Trainwreck Pages by legendary amp guru Ken Fischer, the section on bias adjustment... the safe operational range of EL34 etc. is between 10-40mA per tube... and all amps are different, some may sound better running colder, some sound better with more current at idle. Using Ken's preferred current method... "any current that produces the tone you desire is the "correct" setting".
Regards 🎸