kustom k150-7 reverb problem

[pontiacpete]

This is the 150-7 combo. The reverb works but it's very weak and there is a whistling noise. THe one transistor that had been changed by a previous tech is Q1009. They put in an NTE part , it says NTE123A on it. Looked it up and there doesn't seem to be anything special about this transistor or it's application so it's probably OK. But I keep thinking that this part might not be the correct one for this amp. Can anyone tell what the part is suppose to be here?
Otherwise i"m at a bit of a loss trying to get more reverb out of this, which is what i would expect from this amp.
Any ideas on how to proceed?
This unit uses the PC1000 board for the pre and the PC5032 power board.
Here's the link to 1000: https://docs.google.com/file/d/0B1Fx...?pli=1&rm=demo
And here's 5032: https://docs.google.com/file/d/0B1Fx...UGc/view?pli=1

[DrGonz78]

Right there in the notes "All transistors are SE4002 or PET8002, unless noted." For example, if you search out SE4002 there are threads of people using NTE123A as it's equivalent. I can figure out the NTE123A's correct pinout but still looking to see what SE4002's pinout is...

[pontiacpete]

THanks DrGonz, I sure should have noticed that. I'll get the pin out and see if it's in properly.

[pontiacpete]

I found this thread about the SE4002 and the NTE here, scroll down to JPJazz's post:

Help with Kustom 200



The NTE in this amp was put in the same way the SE4002 was installed. If JP is correct, C and E are reversed.
I tried reversing them and there is no reverb. (BTW this reverb is not weak, it's not happening at all, I think I thought it was weak but i was fooled or imagining it, maybe because the tank was loud and active when banged on, but still there is no wet guitar signal)

Having reversed the C and E to what it is suppose to be the correct way I'm getting nothing out of the tank, even when banging on it.
I'm wondering if the NTE had gone bad because it was put in wrong? Or is this really the correct pin out for the SE4002.
I will trace through the schematic to see what's up with the SE pin out.

[Enzo]

They are just general purpose NPN signal transistors, most anything will work there.

[pontiacpete]

I will try another transistor.
The NTE is now in the right way C and E were in fact reversed.
THe voltages are now:

C - 8v
B - 1.3
E - 6.3

[pontiacpete]

I put a new 2N2222 in and now the tank is alive but still now wet signal.
The voltages look a look better

C - 7.2v
B - -.1v
E - -.5

There's got to be something else. I replaced the only tantalum cap on the E of the Q1009

[pontiacpete]

Looking further. Q1011 a Jfet appears to be working. I'm getting voltage changes when switch reverb on an off.

Q1010 a 2n3638 voltages are:

E - -1.2
B - 8.9
C - 9.6

Is this the culprit?

[Enzo]

Isolate the problem.

First, what reverb pan is in there? Is the input jack grounded? it should be.

Reverb has two halves, the drive and the recovery. The NTE part should have worked, so should a 2N2222. Pull the cord from the reverb pan output jack and touch the tip. Does it make hum out the amp? If so the reverb recovery works. That leaves the drive. No drive means no reverb. Connect the pan and shake it, does the spring crash sound come out the speaker?

Play through the amp, or apply a signal, is ther a string signal at the junction of Q1007, 1008? And after C1020? Is ther signal earlier?

[pontiacpete]

THe reverb pan is a gibbs and the input is not grounded to the chassis.
When I pull the output jack and touch it, I get a very loud screech not a hum.

I check for a signal on Q1007 and 8 at their joining collectors and there is a signal.
Q1020 has no signal anywhere on it.

edit: and the pan crashes when hitting it.

[52 Bill]

THe reverb pan is a gibbs and the input is not grounded to the chassis.

Agree with Enzo it is not the original tank.

Read the resistance of the input transducer it should be at least 50 ohms and the jack must be connected to ground. In order to eliminate a ground loop in the reverb wiring, Kustom disconnects the ground on the drive cable at the pc board.

[Enzo]

The drive side needs a ground return. Otherwise it is like hooking up just one wire to a speaker.

[pontiacpete]

This pan fooled me, looks old enough to be original.. Here's a picture of it and the isolated input jack
Both transducers measure 170 ohms.
I tried connecting the input to ground, nothing
Tried 2 other tanks an EB and FB style(also grounded input)nothing.

[Enzo]

OK, so on the drive cable, make sure the outer conductor goes to ground, then troubleshoot the simple push pull drive circuit.

You have both +8 and -8 supplies? Signal at the bases? Etc.

[pontiacpete]

After poking around with the scope trying to follow the signal, I found that the only signal to be found was on Q1007 and 8 where they join. Using the layout is not easy, it's not very clear which transistor is which, so I start tracing with the ohm meter to figure out what goes where. But the obvious thing finally jumped out... the junction at Q1007-8 is at the input jack. Therefore there should be signal on the tank input. Anyway, I had been using a new right angle RCA cable out of my new pile of them, at least I thought it was new, and sure enough it wasn't making connection. Changed the cable and it works!!
It works with the Gibbs tank and the FB modern tank with no ground connected at the input, contrary to what we have been saying in this thread. No noise or ground loop. Works like a charm. I guess the input doesn't need to be grounded on this amp, obviously. In the schematic it doesn't look like it's connected, no?
It seems that the NTE C and E were reversed which explains why the crash of the tank was very anemic compared to the crash after the 2N2222 was put in correctly.. The RCA cable was bad for some unexplained reason, looks brand new and an OK quality, purchased from CE as usual. I'm going give that cable a close look and see what's up with it.
Thanks to you all for the help!!!