9200 fades out,both sides...

nofearfactor · 11-03-2009, 11:24 AM

This is from a poster who IM'd me over at TheGearPage.

"The volume / sound fades, on the Marshall(9200) power amp, just started. It can be fine at first, but then starts to fades out or go half volume or near zero. It does it on both sides and that puzzles me as I'm thinking power tubes but why would both sides fade".

I own 3 9200s and one 9100 and this has never happened to any of mine but I am curious as to what is causing this to this other fellas amp.

Anybody with any ideas it would be appreciated. Thanx.

Procter2812 · 11-03-2009, 11:27 AM

check the pre-amp valves.

The power amp still use pre-amp valves to drive the power-amp (phase inverter)

Replace them and re-try

nofearfactor · 11-03-2009, 12:21 PM

Ya,but the 9200 is a dual mono amp- 2 seperate totally independant sides. I could see this happening to one side at a time but not to both.

Procter2812 · 11-03-2009, 01:03 PM

Yeah i get what you mean

I cant get ahold of the Schematic... it wont download.

If found a picture of the guts of the 9200 and it looks like it has one phase inverter per side.

Have you looked at the Circuit board for and dry joints. Could be a thermal issue.

Also check the input and connections inside the amp.

Have you any spare pre-amp valves just to try?

nofearfactor · 11-03-2009, 07:07 PM

I have a schematic some where to the amp I could scan to him if he needs it. The amp is not mine. In my OP I stated it was a question from a post'r at TheGearPage who IM'd me knowing I own 9200s. I asked him to check the cables in to the power amp,cables out of the preamp,etcetc. He thinks it may be a problem with the preamp.

I had almost the same problem with an Alesis RA-100 power amp which is a stereo power amp and a totally different setup than the 9200. The relays contact points were in need of repairing causing it to do just about the same thing he descibes but only in one side of the amp.

Anyways. Thanx for the replies.

11-03-2009, 11:24 AM	#1 (permalink)
nofearfactor Senior Member Join Date: Mar 2009 Location: Hellbillyville Posts: 180	9200 fades out,both sides... This is from a poster who IM'd me over at TheGearPage. "The volume / sound fades, on the Marshall(9200) power amp, just started. It can be fine at first, but then starts to fades out or go half volume or near zero. It does it on both sides and that puzzles me as I'm thinking power tubes but why would both sides fade". I own 3 9200s and one 9100 and this has never happened to any of mine but I am curious as to what is causing this to this other fellas amp. Anybody with any ideas it would be appreciated. Thanx. __________________ myspace- http://www.myspace.com/nofearfactor some gear pics- http://community.webshots.com/album/...ecurity=QbSaeN

11-03-2009, 11:27 AM	#2 (permalink)
Procter2812 Senior Member Join Date: Mar 2009 Posts: 333	Re: 9200 fades out,both sides... check the pre-amp valves. The power amp still use pre-amp valves to drive the power-amp (phase inverter) Replace them and re-try __________________ www.sexpistolstribute.co.uk JCM800 2203X JCM2000 TSL100 Marshall 1936 Gibson Les Paul Custom Orville Les Paul Custom Fender Highway One Stratocaster Boss EQ Ibanez Tube Screamer Crybaby Wah Boss TU-2

11-03-2009, 12:21 PM	#3 (permalink)
nofearfactor Senior Member Join Date: Mar 2009 Location: Hellbillyville Posts: 180	Re: 9200 fades out,both sides... Ya,but the 9200 is a dual mono amp- 2 seperate totally independant sides. I could see this happening to one side at a time but not to both. __________________ myspace- http://www.myspace.com/nofearfactor some gear pics- http://community.webshots.com/album/...ecurity=QbSaeN

11-03-2009, 01:03 PM	#4 (permalink)
Procter2812 Senior Member Join Date: Mar 2009 Posts: 333	Re: 9200 fades out,both sides... Yeah i get what you mean I cant get ahold of the Schematic... it wont download. If found a picture of the guts of the 9200 and it looks like it has one phase inverter per side. Have you looked at the Circuit board for and dry joints. Could be a thermal issue. Also check the input and connections inside the amp. Have you any spare pre-amp valves just to try? __________________ www.sexpistolstribute.co.uk JCM800 2203X JCM2000 TSL100 Marshall 1936 Gibson Les Paul Custom Orville Les Paul Custom Fender Highway One Stratocaster Boss EQ Ibanez Tube Screamer Crybaby Wah Boss TU-2

11-03-2009, 07:07 PM	#5 (permalink)
nofearfactor Senior Member Join Date: Mar 2009 Location: Hellbillyville Posts: 180	Re: 9200 fades out,both sides... I have a schematic some where to the amp I could scan to him if he needs it. The amp is not mine. In my OP I stated it was a question from a post'r at TheGearPage who IM'd me knowing I own 9200s. I asked him to check the cables in to the power amp,cables out of the preamp,etcetc. He thinks it may be a problem with the preamp. I had almost the same problem with an Alesis RA-100 power amp which is a stereo power amp and a totally different setup than the 9200. The relays contact points were in need of repairing causing it to do just about the same thing he descibes but only in one side of the amp. Anyways. Thanx for the replies. __________________ myspace- http://www.myspace.com/nofearfactor some gear pics- http://community.webshots.com/album/...ecurity=QbSaeN

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