ptp in jcm 800 worked at first but now probs ???

jbzoso2002 · Post by **jbzoso2002** » Mon May 16, 2005 10:58 am

i have a 50w jcm8oo 2205 from 1983/ split channel rev ef loop
i removed all that put in a ptp 50watt lead board 3 new 50/50 caps
mm plexi opt 10h choke new pots new input jacks x4 in a standard
1987 layout. biased fine fired up with weird sounds. i found that i was
missing a ground fixed that then it was cutting in and out. found a couple
of bad solder joints in the front of preamp. fixed that amp played
but lower 2 input jacks didnt work but i played through the amp for
2-3 hrs sounded ok but with a slightly different overtone on distortion
after a long sustain. rewired the input jacks now amp doesnt play
can hear hiss and hum but no guitar sound bias is still normal
also power trans got pretty hot after the 3 hr playing but it is
20+years old. ive been checking conetions and layout but am
stumped????????????? any sugestions

Billy Batz · Post by **Billy Batz** » Mon May 16, 2005 11:39 am

The tubes can heat up the PT casing alot in some amps.

Can you take a picture? Most of the time a problem with the input jacks has only to do with the input jack wiring. Actually in just about 99% of the time if one jack works and another doesnt its got to be faulty wiring on the jacks.

Guest · Post by **Guest** » Mon May 16, 2005 12:14 pm

it wont let me upload pick it is only 164k ?
let me ask you this can i wire guitar directly to board ?

Dax-The-Ax · Post by **Dax-The-Ax** » Mon May 16, 2005 3:48 pm

You can email me some pics, i'll see if i can post them.

Dax

Dax-The-Ax@cox.net

Dax-The-Ax · Post by **Dax-The-Ax** » Mon May 16, 2005 7:09 pm

Here are the pics. Am i crazy, or are the inputs backwards, or does this not matter.

Guest · Post by **Guest** » Mon May 16, 2005 7:15 pm

I can't tell, is pin 3 and pin 8 connected on V3? They should be.

jbzoso2002 · Post by **jbzoso2002** » Mon May 16, 2005 7:25 pm

yes there connected. ive poured over this thing over and over and cant figure it out. i took another preamp tube and put it in all positions
and still the same thing. the output tubes were in this amp not new
but were working before i changed everything. also like i said
the amp worked like this for 3 hrs except for the 2 lower input jacks
and a slightly weird overtone on the distortion. it had a lot of power
very loud. then i re grounded the jacks so they would all
work and now i have no guitar just a hum that gets louder as
each volume pot goes higher. i dont have anymore el34's to try
and am afraid to take kt66 out of jtm45

jbzoso2002 · Post by **jbzoso2002** » Mon May 16, 2005 7:27 pm

im sorry, thanks dax for posting pics

Dax · Post by **Dax** » Mon May 16, 2005 7:33 pm

I had the inputs wired wrong and only two would work. The Pro's around here can tell you if those are wired properly. I have just never seen jacks facing that way.

jbzoso2002 · Post by **jbzoso2002** » Mon May 16, 2005 7:36 pm

i didnt think that made a difference but on the jtm45 i built they are
faceing the other way. maybe someone who knows will chime in

Dax · Post by **Dax** » Mon May 16, 2005 10:43 pm

i think it's possible that those ground lugs are in a certain spot. maybe you should just rewire them so we know that's not the problem. i had all sorts of wiring problems on the inputs until i studied some of george's pictures.

jbzoso2002 · Post by **jbzoso2002** » Mon May 16, 2005 10:55 pm

he dax whats up? i did rewire them. i had the ground in adifferent place
therenow wired like the examples on the cd except the ears are
pointing towards the pots. im still stumped

i wonder if i damaged the opt ?

i just get a hum that gets loud when the vol is turned up
i checked bias and its fine.

well darn all i have to jam through is a jtm45

Flames1950 · Post by **Flames1950** » Mon May 16, 2005 11:34 pm

Honestly I think the jacks will need to have the lugs facing away from the pots and be rewired accordingly. I believe (and I don't have an empty Cliff in front of me to verify) that only one lug on each contact set is switched when a plug is inserted, so you may not be breaking a connection that needs to be broken when you insert a plug into the jack. I just don't think things will work properly reversed that way, but again I don't have any jacks in front of me, they're all at work.

jbzoso2002 · Post by **jbzoso2002** » Mon May 16, 2005 11:48 pm

thanks flames for your answer. its getting late in these parts nw ind
and i have a bad cold but tomorrow i will rewire these again. if what
your saying is correct it explans it. when the amp was working i had
the grounds on the jacks in a diffent place and the top 2 were working
but the bottom were not. i thought i would breeze threw this amp
build after building the jtm45 with absolutly no probs. oops

ill let you guy's know tomorow what happens.

thanks very much for your help

jimmy

Guest · Post by **Guest** » Tue May 17, 2005 12:35 am

Jimmy, i sent you a wiring diagram for those jacks, maybe it will help. Let's hope!! We can't have non-functioning Superleads around here!!

Dax

Metropoulos Forum

ptp in jcm 800 worked at first but now probs ???

ptp in jcm 800 worked at first but now probs ???

wont let me upload pics?

thanks

input jack direction

jacks