Marshall Lead 12 Combo Manual Transfer
5005 Lead 12; Marty62100's review - Marshall 5005 Lead 12 +. Manual for the ben. But that's a combo and 12 transo. Only at Sweetwater! 0% Financing, FREE Shipping, and FREE Tech Support for Marshall Guitar Combo Amps!
Since I'm more of a tube guy, I don't even begin to know where to start fixing this amp. I have a Marshall Lead 12 combo. I bought it used a few years ago to gut and build into something else, but it sounds pretty good as is and makes a nice light practice amp. The stock speaker really sucks and makes the amp sound crappy. When the crappy stock speaker is replaced with a good Celestion or similar, it really opens up the amp's tone and makes it sound much better.
The mini stack head was used by a lot of the LA guys in the mid to late 80s in rack setups as the tone generating machine, IIRC. It has never really worked right. When I got it the low input channel was intermittent, it would cut in and out while playing the amp.
The high input is fine. I tried reflowing the solder on the low input jack, but this made the problem worse. Now it squeals when the gain is dimed and the volume is turned up. Any suggestions where to begin? There aren't that many parts connected to the low gain input: a jack, a resistor and an opamp. Any ideas where to start to fix this thing?
Schematic is here: The combo is model# 5005, the mini stack is model# 3005. Download Tokyo Game Convention Columbus. Steve, If it were my amp, I would replace both input jacks. There's a muting function on the op-amp output being performed by the 'low' input jack, and a voltage-divider function by the 'high' jack; I don't know precisely what's going wrong in your amp - possibly some kind of positive feedback or the op-amp + input ground reference disappearing - but I'm pretty sure that replacing both jacks will make it go away. I would also recommend resoldering all the component connections around IC1, and in my Lead 12 I pulled the 1458 and put in a socket and LF353 op-amp, which improved the overdrive quite a bit IMO. You could also try cleaning and retensioning the jack contacts; IME the effect of this will last anywhere from a week to 3 months, but YMMV. Update: I got three new Cliff jacks from AES. I replaced all three jacks; low & high inputs and headphone/line out jacks.
Buy Fake Driving Licence. I also replaced all three resistors on the input: 68k, 33k, 330k. Oddly enough the 300k resistor measured 270k as did all '330k' resistors in my parts bin.
Anyway, the squeal is gone. Although there is a split second of squeal when plugging into the low gain input due to the shorting jack opening and then closing to make contact.
BTW, the original jacks were Rean brand. Are these any good? They appear to have been made in England. The low gain input does seem louder than the high gain input with the same master and gain levels.
Thanks for all the replies. Rean jacks are O.K., but I prefer Switchcraft #11 through #14B, depending on the application. Retro-fitting them in an amp with plastic jacks can cause some grounding issues, but that can usually be worked around by rearranging grounds or using isolation washers. The only other issue is space - the Switchcraft jacks are typically larger than the Rean jacks. RE The Cliff jacks that replaced the Rean jacks looked like they were about the same quality. Does Switchcraft make PCB mount jacks?
I like the quality and feel of the Switchcraft jacks over the Rean and Cliff jacks. The Switchcrafts just feel more substantial to me. Thanks for your reply.
The celestions that came in the original 80's Lead 12 stack were actually the 16 ohm G10D-25. They are quite harsh and bright, and very scooped sounding, like a really scooped G12T-75 almost, very fizzy and scratchy, not really much like the Vintage 10 at all.