Marshall 1987S Hiss/Hum Problems

feeds@yuku.com (Tmay) — Thu, 03 Sep 2009 03:02:44 GMT

Hello all, I've finally decided to have a go at fixing my old Marshall which has been plagued with problems from the day I bought it, but sadly my knowledge and experience with amps is woefully inadequate so any help would be greatly appreciated. At the moment the problem is hiss/hum and intermittent volume swells (which may be a loss of high frequencies which give the illusion of a loss of volume) The hiss/hum is only present on the high channel and is not affected by turning up the...

4203 30W Artist.......oscillation??

feeds@yuku.com (mxvin) — Thu, 05 Mar 2009 18:19:28 GMT

Hi guys,
I am trying to work out an issue. The oscillation occurs with moderate to high gain setting and at moderate to high volumes. It happens, for example, when you bend a 12th fret E up a whole step or more. The sustain drops off quickly and the I can hear a "warbling" like sound. Almost like a tremelo effect. This happens in the boost channel and the normal channel. I drove the normal channel with a TS9 to push it.
So far I have: 1) checked the EL34s for bias parity...

Valvestate 80 speaker jack

feeds@yuku.com (dano) — Mon, 19 Jan 2009 20:15:15 GMT

Can any one tell me if the Valvestate 80, (8080) will handle a 4 ohm load. I want to run an ext. speaker cab, but still use the speaker in the amp.

Thanks,
Dano

Marshall VS100 vs VS100R

feeds@yuku.com (Moona) — Wed, 24 Sep 2008 20:23:15 GMT

I'm wondering if anyone can tell me the difference between a Marshall VS100 combo and the VS100R combo. Can't seem to find a comparison anywhere.

Thanks!

Marshall 1987X Rectifier Circuit

feeds@yuku.com (DrewB) — Thu, 04 Sep 2008 19:07:07 GMT

I'm trying to find technical info on Marshall's 4-diode rectification circuit. I think I have rectifier issues in my 1987X. No fuses blew, but it went real quiet. I have 347 volts entering the first pair of diodes and 189 volts coming out of them into the second pair. On the "out" side of the second pair, I have zero. I don't have plate voltage on any of the tubes.

This is new territory for me. Based on my experience with valve-rectified...

Marshall 9005 switches

feeds@yuku.com (jbmojo) — Sun, 24 Aug 2008 12:14:42 GMT

Where can I find the power and standby switches for a 9005 power amp? I've checked a lot of places but they all seem to only have stuff for regular heads, and the "official" Marshall website ain't much help at all.

Muddy tone, jcm800 combo

feeds@yuku.com (MadDave12) — Fri, 21 Mar 2008 19:20:59 GMT

A friend's JCM800 combo seems to have "classic Marshall tone," except it's a little muddy. Not sure how else to describe it... the tone doesn't create the impression that the music is "right there," although it gets plenty loud if asked to.

Does this sound familiar to anyone? Any insights? My best guess is the upper-mids are weak, but that's a wild-assed-guess, at best.

jcm 900 mods

feeds@yuku.com (lostdog666) — Fri, 14 Mar 2008 17:28:06 GMT

I have discharged my filter caps and am now ready to perhttp://www.schematicheaven.com/mods/marshallgainmod.htmform some mods I have found on this site. Ive got the jcm 900 schematics. but not sure of some of the tech talk and where to find some stuff. Like where to find plate resistors to augment the distortion capabilities of my amp. And also not sur but my cathode resistors Is R26 and R27 right?

Marshall TSL100 jumper chart or chassis picture, reverb problem.

feeds@yuku.com (DB Electronics) — Mon, 18 Feb 2008 18:33:39 GMT

I have a Tsl100 in the shop with weak reverb that gets weaker as the gain is turned up and the volume turned down (keeping the same overall volume). Solid state driver and recovery seems to be ok.

My customer bought it on ebay in this condition.

I have a notion that someone along the line may have miswired the jumpers between boards. The schematic only references the jumpers to and from the reverb board, and that seems to be incorrect as it references a jumper socket that...

Marshall

feeds@yuku.com (Skullk1) — Fri, 14 Dec 2007 09:02:37 GMT

Hey guys I just finished building my first amp...its a Marshall 20 watt fully tubes 2 channel amp hand wired..i wondered if you guys maybe know a way that i could make some nice mods to it?maybe a overdrive(distortion) channel?

Wiring for a Marshall 8x10 cabinet

feeds@yuku.com (ronning7) — Sun, 14 Oct 2007 18:34:55 GMT

Hi,
Does anyone have a wiring diagram for an 8x10 cabinet?

I have owned this empty Marshall since I was a punter and have just finished restocking is with Eminence 16 ohm speakers.

I have never attempted to wire up a cab before. I believe it should be wired as an 8 ohm cabinet (based on other threads I read here), I will be running it with a 1980 100 watt JMP

If anyone has any links or diagrams, I would really appreciate it.

Thanks

Gary

Who makes the red rectanglular caps in my '86 JCM-800?

feeds@yuku.com (jmaulz) — Thu, 26 Jul 2007 12:47:04 GMT

Who makes the red rectanglular caps in my '86 JCM-800, and what would be good replacements?
Thanks,
Mike.

Amp picking up Radio

feeds@yuku.com (Storm) — Mon, 18 Jun 2007 10:18:16 GMT

I just replaced all 5 pre amp tubes for my Marshall JCM 800 2210 and now it makes a noise when a cell phone rings in the same room. It also has always picked up a near by radio station, which it still does. Is there anything I can do to prevent the excess noise the tubes i got are Groove tubes?

Also does anyone know which 2 power amp tubes I can pull out to make it 50 watt amp?

Thanks

JTM 45: KT 66 or EL 34

feeds@yuku.com (eardgy) — Fri, 15 Jun 2007 10:43:12 GMT

Hi guitarslingers out there. I think of changing my 60s JTM 45 from the original EL 34 to KT 66. Do you think its worth ? Will any difference be heard ? Regards, eardgy

JCM 800 2210 PreAmp Tube

feeds@yuku.com (Storm) — Fri, 08 Jun 2007 20:58:46 GMT

I have a JCM 800 2210 (two channels) and I would like to replace my pramp tube but I'm not sure on which one to replace. There are five 12AX7 and I'm not sure which one is fot the preamp. Could some one tell me which one to replace.

Thanks
Storm

Any significance between darker and lighter grill cloths?

feeds@yuku.com (jmaulz) — Thu, 07 Jun 2007 21:00:57 GMT

I've notice that some Marshall's like my JCM-800 4104 have lighter colored grill cloths then most. Anything up with that? Just curious.
Thanks,
Mike.

How to bias Marshall jcm-800 50w 4104?

feeds@yuku.com (jmaulz) — Sat, 02 Jun 2007 16:57:03 GMT

I see what I guess is a bias trim pot, but don't see any 1-10ohm power tube cathode resistors to use to determine current. Thanks,
Mike.

Some Interesting Marshall Projects...

feeds@yuku.com (4willieC_nuked_for_import1202780187) — Thu, 28 Dec 2006 11:49:15 GMT

p201.ezboard.com/fthehive...=810.topic

willie
musicmenders.com

trouble with tsl60

feeds@yuku.com (bil71) — Mon, 26 Jun 2006 21:37:01 GMT

I just changed my power tubes, set the bias, then tried the amp. Now for some reason my Lead gain affects my Crunch channel. If the Lead channel gain is all the way down, I get no (or very very little) volume in the Crunch channel and as I turn it up I get all kinds of volume and gain. I didn't think it could be a tube problem, but I put the old ones back in anyway and it's still the same.
All I did was change the power tubes and pull the preamp tubes , wipe them down, and replace them....

tsl60 bias specs

feeds@yuku.com (bil71) — Tue, 20 Jun 2006 20:54:15 GMT

I have a Marshall tsl60 and was wondering if anyone could give me the biasing specs and possibly offer any tips or advice such as the best method for biasing, safe tweaks or mods for different tones, etc., with respect to this model. This is my first worthy tube amp and I plan to maintain and service it myself (I don't want some strange guy having his hands all over her!!!), so I would appreciate any advice. Thanks....

Marshall Amps