Our task was to renovate a June 1973 Marshall Model 1959 Super Lead 100 watt head It had been modified in the 1990’s to use 5881 output valves. This was the time when good quality EL34’s were difficult to source. JCM900’s were using 5881’s in production. A master volume had been added too. The amp had been stored in a garage for 15- 20y ears so it was not a smart plan to switch it
A Marshall JCM900 Breaking Valves was the cause of this amp’s failure. It travels around a lot and it has the original 1990’s valve retainers on the output valves. The original ones fitted to this 4102 model are shown below. These are fitted over the 5881’s to hold them in place. The issue is that an amp is well gigged and in and out of vans suffers a lot of vibration. These holders rub on
A Marshall JCM900 100 Watt Combo arrived in the workshop. This version is the 4102 It was very poorly. The first issues seen were : 10 amp fuse in the plug!! Low power output and VERY loud mains hum Pots noisy Amp plays a dying gasp when amp switched off Pops / crackles and very low volume. The valves were tested on an AVO MkII and CT160 tester. The preamp valves were down to a lot
Note: We now have a new, superior solution to Marshall JCM2000 bias drift issues. Find the details here. The early (1997-2003) Marshall JCM2000 DSL50, DSL100, TSL100 and TSL122 amps are often troubled by an unstable bias (drifting bias). These are nice amps and I have one myself This can be difficult to diagnose correctly, as it can take half an hour or more of testing and/or playing before this Marshall JCM200 bias drift shows up.
Here are Things learned about Tube Amps in 2018 . They are in no particular order. Perhaps some useful info about your amp. I thought I would share them before they faded out of my head Loudness Your ears respond to sound like a compressor. So when you ears hear the sound from a 10 watt amp and a 100 watt amp, you don’t hear an amp that is ten times louder. Your ears hear
We have broadened our range of EL34‘s in our store. But which one is best for my amp? This is a handy quick guide to EL34’s We now have :- JJ EL34 JJ EL4 II JJ EL34L EH EL34 Tung Sol EL34B We offer all the above in matched pairs and quads. The EL34 was one of the last additions to the audio valve market and it was introduced by Mullard in the early 1950’s.
Which EL34 ? We explain differences on selected types Read More »
