Ashdown Peacemaker 20 -Autobiasing? Help needed!!!

Revolting1

Hi everybody.             Bought amp off ebay before discovering this site...... Its shifting a bit in volume,up and down and the distortion when the gain is up is worse than a £25 solid state amp.Tried changing the  output valves(very tired looking JJ el 84s) with  NOS yellow (60's) teslas .That improved the sound a little but also added some hum.Then I looked at the valves and the 84's were gently redplating.                I'm a total newbie with el 84s .             Could it be caused by- mismatched valves?   one or more of the ecc83's ? pin 1 to 2 NOS connection issues?   duff new valves?     "autobiasing"????system"? 

Chinese/Essexmarshgremlins?                                     The geological looking JJs dont redplate.     Is it worth carrying on with this amp,can they sound good.                            This is my first post on the fretboard,I know I've dropped one, please be gentle with me, any help massively appreciated, thanks in advance.                                                                           

ICBM

This probably isn't what you want to hear, but it's also known as the "Partsmaker". Terrible amp, all sorts of problems. It's not likely to be the valves. The only good thing I can say about the 20 is that the bigger models are worse.

Sorry!

I had a quick look on Ebay and saw that at least you didn't pay too much for it - it's probably worth having it looked at by a tech. It's unlikely you'll be able to return it since it was listed with that fault.

And whatever you do, don't let the seller talk you into taking the Failing Angel instead...

DJH83004

Despite ICs misgivings I quite like the Peacemakers in a quirky sort of way, in fact I have still got a Peacemaker 20 that I use as a loan amp. First of all don't get overly concerned by the 'auto-biasing system' it basically means the amp is cathode biased so when you fit the EL84s there is no bias adjustment to worry about. You really need to try a pair of new JJ EL84s in the amp, as they are pretty robust and are ideally suited for cathode biased EL84 amps in my opinion.

The downside to the amp, is the chassis is a pig to get out, as the speaker and baffle have to be unscrewed and moved down to clear the meter & scooped front plate but that means first removing the reverb tank to enable the baffle to slide down far enough! The problem could be one of the pre-amp valves is losing emissions after it has got hot for a while, so worth doing a one at a time swap if you have a good ECC83. Failing that off to the tech I'm afraid. where are you based?     

Edit: Forgot to mention they were actually designed and built in the UK and have fairly decent transformers, better than modern Marshalls IMHO. 

Revolting1

Thanks,                                                                                                                                                                                                      Unfortunately I bought the Frailish ankle 40 at the same time,however that sounds pretty good  so far apart from the dsp effects (no great suprise) and a slightly hissy reverb (is that valve operated?) .                                                                                Could you help me with which ecc83 does what (from the 1 nearest the input jack physically)? and do I need the phase splitter to be gm balanced and non microphonic or is that a myth ?                                Im currently in north west Shropshire, been living "off grid" for 30ish years so mainly been acoustic till recently.Dont know of any guitar techs locally.                                          Gotta few "modern"ecc83's and the odd old mullard but dont want to use an old mullard except in the driver position (unless anyone knows a more appropriate spot).                          Im not up to building an amp but used to be able to build a great narrrowboat outta flat sheet steel.                                               kinda gobsmacked at the angel as it has factory fitted ouput valve covers to give the cooling fan some extra work . Like the tone of that, can the peacemaker sound close if its resurectable?                   thanks  for your time.                     

ICBM

Revolting1 said:

                                                                                                                                                                                                Unfortunately I bought the Frailish ankle 40 at the same time,however that sounds pretty good  so far apart from the dsp effects (no great suprise) and a slightly hissy reverb (is that valve operated?) .                    

No, it's solid state.

Revolting1 said:

Could you help me with which ecc83 does what (from the 1 nearest the input jack physically)?

The first one is the initial gain stage for both channels, the second is the second gain stage for both channels, the third is the third and fourth stages for the overdrive channel only, and the fourth is the phase inverter.

Revolting1 said:

do I need the phase splitter to be gm balanced and non microphonic or is that a myth ?                

No, completely myth. It doesn't need to be balanced, and the valve most prone to microphonics is V1. The phase inverter is the one that matters *least* for microphonics and noise.

Revolting1 said:

Gotta few "modern"ecc83's and the odd old mullard but dont want to use an old mullard except in the driver position (unless anyone knows a more appropriate spot).          

Try the Mullards anywhere, especially V1.

Revolting1 said:

kinda gobsmacked at the angel as it has factory fitted ouput valve covers to give the cooling fan some extra work .          

Yes, they're very poorly designed - and as DJH said, an utter pain to work on since that extends to the physical build as well!

DJH83004

The Fallen Angel 40 has a dsp reverb which it is inherently noisy, these were Chinese built amps and not the greatest quality.
If you get hold of a Peacemaker 20 schematic off the web (or a 40/60, as the front end is pretty much the same), V1 nearest the input jack, triode halves A/B are a common input stage for both channels.

V3B is channel one tone stack driver, V3A is channel two tone stack driver. V5 A/B are the extra gain stage on channel two which also provides additional boost (channel three) - that does sound awful BTW.

The reverb and effects loop are IC driven (TL072s). V7 is the PI, and no don't worry about it having matching halves, its just not necessary.

I don't know any fellow amp techs in your area I'm afraid, I'm based in Nottinghamshire, which is a bit of a trek!     

Revolting1

Wow                            Very comprehensive answers,much appreciated, good to know that at least one amp is potentially reliable-   will give it ago with the ecc83's.    If I lose the valve covers and fit socket savers  will that cause any issues(RF etc)?   Thanks

ICBM

Revolting1 said:

good to know that at least one amp is potentially reliable

I'm not sure I'd go that far , but the Peacemaker is definitely the better of the two.

DJH83004

I agree with IC, concentrate on getting the Peacemaker sorted out first, then you can do a direct comparison between the two.   

Revolting1

Sorted the volume shifting issue- it was th Tonal Audio Disaster in v1 position.         Gotta well rounded sound on the channel 1  Channel 2 still sounding worse so will keep swapping valves to get some bass in channel2 and a decent sounding drive if possible,got some NOS RFT's somewhere............................               Presume is ok to do a continuity check between pins 1 and 2 on the output valve sockets (looking downwards) to see if that was causing the redplating issue with NOS EL84's                                   Big thanks to IC and DJ for the info

DJH83004

I think you are referring to the potential problem where some amplifier manufacturers use pin 1 as a wiring junction point, which is fine with modern EL84s but not certain NOS valves as they have an internal connection on pin one?? With the Peacemakers, they use a PCB mounted valve socket, and I am sure pin one is just soldered to a standalone pad. If in doubt just use modern EL84s.

Revolting1

                   Thanks DJ   -   Exactly that,thought it might be causing the redplating with the vintage NOS Teslas,been using what I've got to hand. Does your amp do low volume well? this one is great on channel  1 with a bit or lots of volume but still harsh and brittle sounding on channel 2- is that normal with these?            

DJH83004

They do a reasonably decent clean sound from channel one, but the gain/overdrive channels do leave a lot to be desired, probably better just using channel one plus your O/D pedal and forget the rest