View Full Version : Help marshall jtm 60!!!!!!????????

07-03-2009, 10:40 PM
Help marshall jtm 60!!!!!!
I have had this amp that i got used for about 2-3 years decided to change tubes and did so. man told me how to bias it with a multimeter???? done what i was told by checking across the only pot on the power board that shorted something tubes went extra hot i killed the stand by or power i cant rember fired it up again poped fuse.... got my self a rash of spares and started my novice tech work... turned down the pot and re tubed her had a slight buzz for several hrs but worked rather well. maby played 20hrs oh i should mention i have had high pitch feedback that is uncharacteristic of this rig...then all of a sudden it dies. well not exactly i can hear maby 2% volume all clean/dirty reverb ect seems in order it just has no power.main transformer seems ok i swaped power tubes with others and have the same condition.. caps,rectifier,heater????? any sugestions graciously accepted.Thanks in advance..101

07-04-2009, 08:13 AM
Despite the myriad of design flaws with that amp I have really liked the sound and feel of the couple that have passed thru my shop. Please don't be offended but you should take the amp to a tech. Sounds like you started by shorting the bias supply and red plating your tubes.

07-04-2009, 08:57 AM
i agree that i probly goofed with the help of some bad advice and am verry intrested in learning how to repair this myself with help from willing people who know amps i do exelent solider work and know fair amount about other eletronics no parts in there i cant replace for a few dollars..i used to know this great teck but some how lost him. my labor is fee to me plus i enjoy the education. any parts to check or formatable test to run on them will be greatly appreciated.thanks in advance for any help 101

07-04-2009, 09:08 AM
First thing to do is take voltage readings from the tube pins...

07-04-2009, 09:16 AM
It`s design is flawed. My bud and amp tecks have been trying to fix his for years. He should have just moved on and saved $ and grief.

07-04-2009, 03:29 PM
thanks every one ill take other suggestions also i hate to part with this one, love the tone. this is a head and i have a 4-10 fender open back cab witch i culled a 4-12 85w celistion cab for i enjoy this amp when it is working properly. I just want to learn how to keep it on the road myself ive known some verry good and reasonable tecks but do not know where they are now plus with the exception of one i knew would take a long time. thanks again 101

07-06-2009, 01:31 PM
ok guys n gals effect jumpering had no efect on the condition of this rig the bias pot checks ok but the tubes do not respond when it is turned they look as if in a low power state they are glowing but not much .

07-07-2009, 11:47 AM
I second the motion that these sound great (when working). I had one, and I got the most awesome Zep tones out of it, but read about their dubious reliability, and sold it...

Good luck with yours. Did you check the voltages at the pins?

07-07-2009, 12:04 PM

You already had a thread about this. Why did you start a new one?

07-07-2009, 01:13 PM
I am newer to forums as i am amp repair i am only trying to gain some info on how i might fix this sorry for the inconvince..and thank you for your response..101

08-03-2009, 07:29 PM

08-04-2009, 02:25 AM
Have you taken the voltage readings off the power tubes?

08-04-2009, 03:49 PM

bump for what?

EDIT: I just saw you started yet another thread, and posted some whacky numbers there. All I'm going to say is you are WAY over your head

Peace?????????????????, out!!!!!!!!!!!!!!!!!!!!!!

08-04-2009, 06:19 PM
thanks for your in put i bumped this trying to do the forum a favor sorry about the wacky numbers ill fix this amp with or without your help russ b

08-04-2009, 07:45 PM
thanks for your in put i bumped this trying to do the forum a favor sorry about the wacky numbers ill fix this amp with or without your help russ b
My intent here is to inform, not inflame. I think RussB merely meant that you have started 3 different threads on the same amp/problem (which is somewhat akin to shouting over everyone else to get attention for yourself), gotten advice that you haven't yet responded to (tube voltages), and posted some difficult to make sense of information. The people on this forum are very helpful for the most part. The responses I've read to your posts all seem to be made with the best of intent. Tube amps can be very confusing when you first get into working on them. It's easy to make mistakes that can be costly, and dangerous. It would probably work best for everyone if you confined your posts on this topic to one thread. You might even ask a moderater if you can condense or delete your "excess thereads". That would enable us to see what other have posted, and help you better. http://www.thegearpage.net/board/images/icons/icon7.gif Peace!


08-08-2009, 04:08 PM
I am appoligetic over my newness to forum structure. I have made attempts to bump the threads and somewhat consodilate them sorry i sent the tube voltages in a pm i found out also a no no the only thing there wrong was -b low thanks i perhaps was overzelous in trying to get info and didnt know anything about how forums worked (the reason for the many threads) nothing intential i also think i have responded to every post some trough pm OOPS and at least with a thank you . I am verry appreciative for all the advice and knowledge that comes from this site. THANK YOU! And for the time these experts take to answer my stupid questions also another big THANKS TO YOU GUYS.

08-08-2009, 07:37 PM