Help with JTM 60

[iceman0124]

Hey guys, longtime marshall owmner, first post.

I've had a JTM 60 since the mid ninetys (bought new) and it served me well for many years, it started sounding kinda stale about 4 or 5 years ago, and since I wasnt doing anything with it other than jamming around the house, I bought a little vox moddling amp. I'm playing again now and wanted my marshal roar back, I cleaned the amp really well, and romoved and claned the tubes, when I fired it up it sounded perfect...and did for several days till today.....the volume was a lot lower, and not near as punchy sounding, looked at the back and the first power tube was dead, I had a hardly ever used set of EL34's (same as whats in it now) and swapped those, it fired just fine in standby, however the first output tube got near meltdown within minutes.....so I shut it down, let it cool and tried one of the original tubes with the replacement that didnt overheat, so far so good, its a different brand and glows a different hue, the orginal tube is a whiteish orange where the replacement is a deeper orange. It sounds great, breaks up a little quicker, and no noticable hum or what not, played around 30 minutes without issue. Main question is.....is what I'm doing a bad idea? If so about how long could I safely get away with it? i'm out of work due to a major spinal surgery and moneys tight, it'll be awhile before i can get the scratch to replace the power tubes +1 12ax7 +biasing.

Any thoughts and advice are appeiciated.

 

[steelhorse]

Sure it's better to go with matched tubes but imo soon as you fire those babies up they're probably no longer as matched anyway.

I've mixed different brands in the past so long as the bias is good all should be well.

If it sounds good and nothing bad is happening then there's a good chance that everything is fine. To be on the safe side and potentially extend the life of the power tubes it would be a good idea to check the bias.

 

[iceman0124]

I think I might just bite the bullet and retube.....its only happend once, but the audio dropped out for a second or two....then came back, it wasnt slow, but it wasnt an instant on, its never done that before, played it about an hour after with no ill effects.....but I dont want to break my amp.

 

[steelhorse]

Bob over at Euro Tubes has some great kits, decent prices and friendly advice check them out if you need a supplier.

 

[st.bede]

Euro Tubes.

+1 They have given me a lot of good advice

 

[iceman0124]

thats a neat site, though I'd still rather have a friend of mine that builds amps bias mine for $25 bucks. Right now I'm kinda torn by what pramp tubes to get, ruby ecc83's, or some higher gain Electro Harmonix 12AX7EH's, I'd like a little more saturation, but I also dont want to lose the glassy cleans that made me buy the JTM 60 in the first place.

 

[steelhorse]

Precisely why a brief chat with Bob might be a good thing! He can suggest just the setup for your needs

 

[iceman0124]

Yeah, I'd just feel bad about likely not buying from him due to the fact that I want to be up and running at full bore tomorrow morning, I think I'm just gonna stick with ruby EL34's/ECC83's....the cleans cant be beat, and pedals can take care of the blistering distortion....when in doubt go with what you know.


Thanks for all the advice!

 

[iceman0124]

Actually I think I am going to buy from him, sent him an email and we'll see what he says.

 

[steelhorse]

Let's us know what you decide and how it turns out!

 

[iceman0124]

It may not turn out....after 13 years or so of trouble free operation.....its one thing after another, after reading all the info on the site you reccomded I cleaned the tube contact thoroughly, and on a whim tried the power tube that quit working, and what do you know, fired right up, played around with for 5 minutes or so and the volume dropped out, only this time it didnt return, looked at the back and the power tubes were glowing, however the preamp tubes werent, turned it off and let it cool, turned it back on and they all fired, after about 10 minutes the volume dropped, the power tube in the other socket was out... Talked to my amp guy and has some ideas on what the problems "could" be, but with diagnosis, the cost of tubes, and if its the simple type problem, I'll be looking at $250ish....if its a more impressive problem, a good bit more. The cost plus the fact that the guy that would be doing the work is swamped starting up a very cool guitar company, J. Backlund Designs (he was also the founding father and orginal designer and luthier of Warrior basses, I own one of the original prototype 6 string electric guitars) its going to be quite awhile before he can do anything serious with it, a straight retube he could get done within a week, this he told me would be a month or two at best. So now I'm considering looking for a cheap, reliable low wattage tube combo of some sort in the $300 range, any suggestions? I can get a new orange AD5 for around $400, but thats a little over budget and smaller than I'd like, 15 to 30 watt would be ideal.

 

[iceman0124]

I'm still up in the air on what to do....i've been offered a crate V-33 head for $100, its tempting, the amp has an impedance of 8ohms, where my marshalls speaker is 16, would that be okay to run together?

 

[steelhorse]

I don't think so.

 

[iceman0124]

Think I'm gonna just shelve it for now, I dont have the money to gamble on something that may or may not work out. Toyed around with the idea of picking up one of those insanely cheap crate V series amps, but I'm leery of them. I have a friend who has a Hartke GT100C he said he'd sell me for $100 flat, I might check it out. 100 watt SS poweramp with a tube driven preamp, 2.5 channels,clean with a switchable boost and high gain with 2 12"speakers. I've never heard it but he raved and raved about it a year or so ago when he got it, but then he switched to straight up acoustic about a month later. I've been doing some research on it ( Iwasnt even aware Hartke made EG amps, just bass and acoustic) and reviews are sparse but mostly positive. The main good/bad feature common to most reviews were the controls are ultra sensetive, IE every slight twist of a knob makes a very noticeable impact on your overall sound, in my mind I see this as a good thing, in practice it might not be.On hartkes site they reccomend keeping a record of the sounds you like. One big question if I go for it, with the hybrid amps, does changing out the premap tube make a big difference in overall sound, some of the reviews state that putting a high gain tung sol in plaice of the sovtek opend up the sound dramatically, the guy I bought it from said that he was told that as well when he bought it and planned on doing that, just stopped playing electric before he got around to it. The amp in question uses the tube in what they call a "bootstrap circuit" they dont explain it, but a best educated guess from someone i talked to that knows a fair amount belives that it allows the tube to color the overall sound, and not just the high gain channel like a lot of single tube hybrid amps do.

Heres the amp, it looks killer for the price, though I've seen it new in closeouts for just double what I can get it for used, my friend said he paid $350 or so for it about a year ago. I like the little tube viewing window.

http://www.samsontech.com/products/productpage.cfm?prodID=1793&brandID=3

Sorry for the book and topic derailing... and thanks again for all the help

 

[steelhorse]

If you're gonna spend that kind of money why not pick up a used or even new Vox AVT30? Those little things are off the hook imo and they do come with a pre-amp tube that I upgraded to a JJ (I also upgraded the speaker, but that's just me, it didn't really need it).

I got mine on ebay for 150 bucks.

There are reviews on Harmony and MF and all over the web check it out.

 

[iceman0124]

I have a vox DA 15 as a bedroom noodeler, I dont want a moddling amp for my main amp. Basically I want a good loud soild clean tone that I can manipulate with a digitech RP 500 in stomp box mode (all amp/cab moddling disabled) set it and forget it

Did you notice any real difference with the tube change on your vox? I'm gonna give the hartke a test drive in a day or two and see how it pans out, I havent commited to anything yet.

 

[steelhorse]

The AVT30 is a capable gig amp and I did notice a difference replacing the tube. It became warmer with a nicer distortion.

When patching it into the house PA it kills. We all kinda looked at each other and all we could do was laugh it was so cool for such a little amp.

Since you're not gigging anyway this would be a good investment imho.

Never heard or tried a hartke.

 

[iceman0124]

I plan to be gigging soon, thats why I brought the marshall back into service, just in a big financial bind at the moment. Just have to see how the test drive goes.

 

[steelhorse]

Oh, I gotcha now. If you're gigging I'd just repair the amp, but I understand your tech is busy.

 

[iceman0124]

Time and money always seem to be my worst enemy.