Peavey Classic VTX problem

[Enzo]

Without more specifics on what the low reading was and between which pins, I still have to say that if two transistors in identical circuits side by side measure substantially different from one another, then one of them at least has a problem.

Those transistors should be replaced in pairs anyway, so if one is bad, replace both.

[Enzo]

Without more specifics on what the low reading was and between which pins, I still have to say that if two transistors in identical circuits side by side measure substantially different from one another, then one of them at least has a problem.

Those transistors should be replaced in pairs anyway, so if one is bad, replace both.

[drewl]

The one with the "low reading" as you stated, is probably bad, shorted between pins due to high current draw.
Pull them out and check them, or just replace them.
Also check Q4 and Q5, the 6530's that feed Q6 and Q7, you will need to pull them out to check them properly as they have 47ohm resistors on their base, so they will have a "low reading" in the circuit.

That's what was wrong with the one I just repaired.
Bad output tube killed Q6 and it's feeder Q4.
Don't forget to check all the components in that circuit, resistors, diodes etc.
I replaced all four of those output devices, as well as the output tubes and the amp works correctly.

[dylan08]

I'm going to replace the transistors. will these ones work?
VOLTAGE REGULATOR ( FIXED ): TYPE: 7805 | Semi Conductors/IC's | Ratings & Reviews | TheSource.ca
AMPLIFYING TRANSISTORS | Semi Conductors/IC's | Ratings & Reviews | TheSource.ca

[Jazz P Bass]

I'm going to replace the transistors.

Which transistors are you replacing?
Q?:

[Enzo]

NO!!

That 7805 in your first link is not a transistor, it is a 5 volt regulator IC.

The schematic calls for a 5884 (that is a house number) as the cathode transistor. A good substitute for that is the MJE15030 or MJE15032. Mouser sells those.

[Enzo]

NO!!

That 7805 in your first link is not a transistor, it is a 5 volt regulator IC.

The schematic calls for a 5884 (that is a house number) as the cathode transistor. A good substitute for that is the MJE15030 or MJE15032. Mouser sells those.

[oc disorder]

think this got missed from the first post

http://soundcloud.com/dylanmn/straight-in

by DylanMN on SoundCloud - Create, record and share your sounds for free

Also again I mention this link http://music-electronics-forum.com/t16601/
the second photo down shows what Bushman80 replaced his 5884's with which were MJE1530.
As Enzo said they can be replaced with either the MJE15030 or MJE15032 .

They just happen to be in the same style package as a regulator so look like them.

After listening to the clip, to me it doesn't sound like only half of the signal...~ but on low volume perhaps!

[dylan08]

so I guess I will replace Q6 and Q7 with MJE15030G ON Semiconductor | Mouser
what about Q4 and Q5? I might as well replace those too. I was looking at that other thread and it seems I should use these. 2N3904 Central Semiconductor | Mouser
So if i replace all of those parts, do you think it could solve my problem?

[oc disorder]

I think the probability is high...

From your discussions with Enzo and seeing you had different readings on the transistors pointing to a failure there and
providing the tubes and speakers are ok I think this will probably fix it.

Also seeing others have had problems in this area its pointing to a good result.

Of course there are always things like cracked circuit boards and other components which can also go wrong.

Regarding the 2n3904's as they don't cost much and Mouser also stock them you may as well get them while you are there.
Can't tell from here if they are faulty!
At least you will save on postage/shipping even if they are ok

[dylan08]

The parts came in today. I was impressed with the shipping. It only took a week, I live in a small rural area in canada so I am used to waiting 2 -3 weeks for online orders. I replaced the parts and it seems to be working. Thanks for all the help I really appreciate it!