Unprofessional mod done?

[ThatMarshallGuy]

I am considering buying this Marshall Jmp 2203 1979 but I had the guy send me picture and there are 6550 tubes where there should be EL34's and the parts to hold the tubes in (I don't know what theyre called) are missing. Can those parts be easily found and what are the damages done if an amp meant for EL34 tubes is running 6550s without any work done? Thanks.

 

[GKR1]

Overseas models were usually equipped with 6550 due to a shortage of el34 tubes. Some guys prefer them to 34s. Its all good. Its not a mod.

The tube holder springs are not hard to find or replace. It might set you back $50 bucks.

If the amp sounds good, buy it. The filter caps seem to be in good shape visually.

 

[ThatMarshallGuy]

I thought voltage selector and two loudspeaker outputs would mean its not an overseas model?

 

[ThatMarshallGuy]

And even if the amp was shipped with 6550 tubes it would still have the tube spring retainers. That's why I think its a mod as it looks unproffesional

 

[Rokinroller]

Looks like its been hacked around with by a hack . The guy "thinks" that phase inverter 12ax7 tube right next to the power tubes is a "preamp" tube . Unless it was modded in a weird way , the 12ax7 FARTHEST TO THE LEFT of the power tubes is always the 12ax7 PREAMP tube. Inside gut shots would tell us more. But there seems to have been a hole drilled on the rear panel as well , so that amp looks hacked up from its original state in more than one way , which kills its value.

 

[ThatMarshallGuy]

I just decided not to go for it. I don't want to get stuck with a ruined amp that needs work no matter how good a deal it is. Hopefully another one of these comes by soon as I really really want one. It looked a little fishy that's why I hesitated.

 

[dreyn77]

you know where these things will endup soon?
cause nobody else will see the instant value of them.

the antique shops. the guys who flog old stuff nobody else is prepared to put into their shop.
then this kinda amp will just sit there for sale year after year, without being fixed and the price will keep going up, just like the old clocks and radios and sliverwhere and LP's and fireplace tools and etc....

the people who have money and realise this old stuff is wanted by somebody will pay a bit and then just sit on it for a long time.

they're sitting on loads of guitars, so it's only a matter of time till the amps end up there too.

all they need to do is put a sign on it that says "as is". so it's upto you the buyer to fix the amp.

The individual seller can't sit there for years never selling the item.

there's 8 times more antique shops here than there is new music retail or pawn shops, s/h music shops combined.

they need lots of stuff to bring in the customers.

If this amp falls into the hands of those people, you're in for a long wait and at the end you'll still need to fix everything yourself.

the only reason the price might lower is if the shop people decide to retire.

Eventually people get forced to buy new stuff, cause these business's enter the game buying up all the household stuff with any tiny amount of value.


so you might need to decide, that old stuff needs fixing, today and every day for the next 30 years.

the pro would have more than 1 amp. this IS the pro amp, no doubt.

 

[dreyn77]

maybe you need to ask yourself, "how many amps have the sound of this amp?"

the answer is NONE. just these particular models.
sure the other amps have a preset sound which seems to act the same but it's not the same.

just like the 70's guitars have their own unique sound from other eras, the amps too are unique.

so 90% of your amp model marketed items will all need big dollars spent on them.

luxury items and they always were. they just happend to fall into the hands of people who ruined them for a while.

 

[blues_n_cues]

Overseas models were usually equipped with 6550 due to a shortage of el34 tubes.

actually,it was because the 6550's stood up to shipping better,or @ least that's what I've read several places over the years.

 

[ampmadscientist]

I am considering buying this Marshall Jmp 2203 1979 but I had the guy send me picture and there are 6550 tubes where there should be EL34's and the parts to hold the tubes in (I don't know what theyre called) are missing. Can those parts be easily found and what are the damages done if an amp meant for EL34 tubes is running 6550s without any work done? Thanks.

You need pictures of the inside.
Nobody would have a clue unless they could see the internal wiring.

6550s are OK. There is only a small difference from EL34 wiring.
Somebody drilled a hole for a (?), but that's not in there anymore.
Tube retainers are cheap and easy to buy.
Labeling phase inverter "preamp" means little or nothing...

You wouldn't know what else was done without photos.

And granted, it probably needs recapping, and a few other things.

Potentially, a great amp. Depends on what somebody did to the inside.

I would ask for the pictures and go from there. Could be a winner.
There is nothing in the 2 pictures to indicate a bad mod was done.

 

[Ken]

Everything has a value at a price...if it works and sounds great, there's no reason not to buy it if the price is right.

Ken

 

[roycaster]

Unless you’re collector; the important question is what does it sound like…

 

[ThatMarshallGuy]

My problem wasn't that it was modified. I'm not looking for a collectors piece. My problem was if it wasn't properly configured to take 6550 tubes and it originally had EL34s, I don't know what kind of damage that could cause to the amp.

 

[temporarychicken]

Is the amp working reliably or is it spares or repair?

You could always convert back to EL 34 if you wanted.

 

[Rokinroller]

That's why I don't buy fleabay for example. Whatever used gear I buy has to be close enough for me to go over and check it out myself in person.

 

[ThatMarshallGuy]

Do any of you know though what damage occurs if you were to take an EL34 powered amp and just plug in 6550's without doing anything other than maybe trying to bias them? and vise versa?

 

[roycaster]

Most of the Marshall’s of the ‘70s and ‘80s have been modified at one time or another. That is the way things were back then. If you’re in the market for an amp that hasn’t been touched, be prepared to pay a premium. These amps are pretty basic electrically, it shouldn’t be that big a deal for a competent tech to put one back to stock if it has been modified. These amps are getting on in years; you’ll probably want a tech to look over any amp you purchase anyways…

 

[jakub421]

Do any of you know though what damage occurs if you were to take an EL34 powered amp and just plug in 6550's without doing anything other than maybe trying to bias them? and vise versa?

Little to no damage if 6550s are biased correctly. Grid leak resistors may be changed, but it isn't necessary.

Also, there is a very good chance that this amp did originally come with 6550s, so it may already have the bias range and grid leak resistors used for 6550s. Look up "convert 6550 to EL34" and you'll find tons of threads on this mod.

 

[Masliko]

Alot of people just through in tubes without biasing in the 70's.As far as i know it wont hurt it,it will just sound like **** but the speakers is another story from ****ty mods.

I would stay away from this one.I have seen alot like this and you'll spend thousands on all the cabs, it would possible blow.

 

[jack daniels]

Overseas models were usually equipped with 6550 due to a shortage of el34 tubes. Some guys prefer them to 34s. Its all good. Its not a mod.

The tube holder springs are not hard to find or replace. It might set you back $50 bucks.

If the amp sounds good, buy it. The filter caps seem to be in good shape visually.

I'd really like to hear the lowdown on the switch from EL34 to 6550 tubes made by Marshall/Korg/Unicord. I believe it was Aspen Pittman of Groove Tubes that said it was sub par quality EL34's that Marshall was using at the time, and the EL34's didn't last past the vacuum tube warranty period and it was coming out of Marshall's pockets. Other sources (most likely Unicord) said it was due to the EL34's not traveling well (i.e.) breaking during transit. How many Marshalls were sold all over the world pre and post 6550? A helluva lot more Marshall EL34 models I'm sure.

One only has to reflect back to Hendrix's day and his usage/preference for 6550's, and then the metal era not long thereafter when many thrashers preferred 6550's over EL34's for that added headroom and bottom end prior to clipping. The initial reason given for the tube swap appears more likely (increasing demand and sturdiness/durability) of 6550's over EL34's. And lastly, I remember hearing Aspen Pittman's explanation of Marshall's reasoning way before I ever heard of Unicord's take on the same issue.