New JTM45/100 Hendrix spec

[Joe Popp]

Finally finishing up my JTM45/100. It has some issues I still need to sort out.

- The V6 power tube is red plating (yes, just one!)
- DC leakage coming from somewhere resulting in crackle/static

I used a ton of NOS vintage stuff and I am beginning to think this is not the way to go for certain components.

She looks pretty but still needs some sussing out.

Haven't been here for a long time so nice to be back!

[fixer2]

Where did you get the specs of a hendrix amp ,just like to know I want to make a second one soon after I get this jtm 45 figured out,probley build more in the winter .Nut what link did you go to .

[Doug H]

Cool, I've been sitting on bags of parts for one of those for a while now. I think this is the winter lol.

I see you went the full monty on all the old caps , even in the bias section!

[axeman]

Check the swamp resistor connection on V6 and or readjust the tube.

[neikeel]

Cool, I've been sitting on bags of parts for one of those for a while now. I think this is the winter lol.

I see you went the full monty on all the old caps , even in the bias section!

They look like new RIFAs to me.

Axeman is right check and double check your socket connections and grounds. I presume the problem does not follow the tube when you switch around?

[Joe Popp]

Hey Metroers! Good to be back.

I am just digging in on this. I moved the tube and it does follow so I have a bum tube. I bought them a year ago so even though they are "new" I have no warranty past 90 days. I will start with that first.

Neikel is correct. The RIFAs are new and purchased from Valvestorm.

The NOS stuff used are all of the Piher resistors, the mustards, and that big Blue Erie on the board.

I had a very similar problem with crackling on my last JCM800 build that turn out to be a bad Radio Spares (NOS) mica in the tone stack but the micas in this build are new. Doesn't rule them out...

Once I get the new power tubes I will start sorting the rest. Thanks so much for all of the support!

[Joe Popp]

Where did you get the specs of a hendrix amp ,just like to know I want to make a second one soon after I get this jtm 45 figured out,probley build more in the winter .Nut what link did you go to .

I found a layout on the Marshall Archives here:

http://www.amparchives.com/album/Marsha ... 0Amp).html

[Joe Popp]

Finally getting some time to dig in again on this amp. I fired it up and I am not getting any bias reading from the last two power tubes (V6 and V7). So obviously after a short time the two tubes being to red plate. I checked all of my connections. and can't find anything obvious.

Here is the layout I am using:
http://www.joepopp.net/joe100/66%20JTM4 ... 4000PX.jpg

[Joe Popp]

update.

V7 is getting super hot quite quickly. Faster than V6. I swapped these tubes with some fresh one. same result.

I heard an odd ticking when I fired the amp up like almost like an arcing sound. Ugh.

I am sure there is something super simple I am missing. Reflowing the bias circuit.

[axeman]

I need you to clear some confusion, on your speaker jack, it looks like you grounded the hot side, also is the yellow wire from the screens going to the top of the 10k resistor? and how is your negative feedback hooked up. it looks like its going to v3 cathode ??????? I don't know

[Doug H]

I think the black heater wire just looks like it's connected to the speaker jacks. It does look like you connected the screens to the PI power node, that would probably cause some grief if it's the case.

I know it's a dumb question, maybe it's too early, but wtf is the red and green twisted wire that runs off screen?

[axeman]

The green and red wires are primary wires.

[Doug H]

right, the wires between v7 and 8 is the PT secondaries. The amp wasn't completely assembled for this pic then.

[neikeel]

update.

V7 is getting super hot quite quickly. Faster than V6. I swapped these tubes with some fresh one. same result.

I heard an odd ticking when I fired the amp up like almost like an arcing sound. Ugh.

I am sure there is something super simple I am missing. Reflowing the bias circuit.

Check the grounds out on that tube, make sure no dry joints, possibly replace the flying grid resistor between v6 and V7 if nothing else amiss.

[syscokid]

...She looks pretty but still needs some sussing out.

Haven't been here for a long time so nice to be back! ...

Can't help you with your hiccups on your amp, but that does sure look pretty. I like the braiding from the OT to the Back Panel...