Home » VintageKustom.com » Repairing Kustom Amps » Kustom 200 B1 blowing fuses (200 B1 circuit restoration help needed)
Re: Kustom 200 B1 blowing fuses [message #21615 is a reply to message #21614] Thu, 02 October 2014 18:51 Go to previous messageGo to next message
Tone Meister is currently offline  Tone Meister
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I used a FREE image hosting site (Photobucket) and copied and pasted the IMG code into the text area.

Double-click the picture I posted and you'll see what I mean.

[Updated on: Thu, 02 October 2014 18:52]

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Re: Kustom 200 B1 blowing fuses [message #21618 is a reply to message #21094] Thu, 02 October 2014 21:30 Go to previous messageGo to next message
chicagobill
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Looking at the hole pattern in the board it looks to me like the collector and the emitter leads have been reversed. Check the schematic, the emitter of Q710 connects to the 4K7 resistor, does it? The collector should connect to the 10K resistor, does it? I would go back and double check all of the transistors that you have replaced and be sure that they have been installed correctly.

If you look at the all of the original round plastic transistors, there will be a flat spot along the outside edge. The lead closest to the flat spot is the emitter.

What is the new resistor that just out of frame, 10 ohms? I also notice that your R743 is 1K2, it should be a 1K8.
Re: Kustom 200 B1 blowing fuses [message #21619 is a reply to message #21094] Fri, 03 October 2014 07:23 Go to previous messageGo to next message
Tone Meister is currently offline  Tone Meister
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Good eye, Bill on spotting that 10 ohm resistor. It's actually three 10-ohm Rs in parallel to make up the 2.7-ohm R that was there in the regulator. I actually replaced both R745 and R751 this way.

Looks like I am gonna have to take a real close look at all 6 of those transistors I replaced. All the transistors in the negative rail blew (Q715, Q716, and Q717) but everything seems ok on the positive side. I'll meter test them all this morning and find out for sure.

My buddy who owns this amp is driving down tonight from VA and I'd like to send this back with him in the morning. He'd be thrilled if it works the way it should. He's the original owner ...
Re: Kustom 200 B1 blowing fuses [message #21620 is a reply to message #21618] Fri, 03 October 2014 07:55 Go to previous messageGo to next message
Tone Meister is currently offline  Tone Meister
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chicagobill wrote on Thu, 02 October 2014 21:30
... I also notice that your R743 is 1K2, it should be a 1K8.


Bill,
I'm not sure which schematic you're looking at, but my board is a PC-703 and on the schematic I have R743 is 10K and connects to the base of Q711. In fact, I don't see a 1K2 or a 1K8 resistor anywhere in the regulator section of my schematic.

http://i871.photobucket.com/albums/ab276/ResidentToneMeister/B1Regulator_zpse76be086.jpg~original

http://i871.photobucket.com/albums/ab276/ResidentToneMeister/IMG_3108_zps8f945f23.jpg~original

[Updated on: Fri, 03 October 2014 08:08]

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Re: Kustom 200 B1 blowing fuses [message #21621 is a reply to message #21094] Fri, 03 October 2014 08:35 Go to previous messageGo to next message
stevem is currently offline  stevem
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It would seem that Bill is looking at rev 2 of that 703 board.
Re: Kustom 200 B1 blowing fuses [message #21624 is a reply to message #21094] Fri, 03 October 2014 12:02 Go to previous messageGo to next message
chicagobill
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On your schematic R742 is 1200 or 1K2 ohms.
Re: Kustom 200 B1 blowing fuses [message #21626 is a reply to message #21094] Fri, 03 October 2014 12:09 Go to previous messageGo to next message
Tone Meister is currently offline  Tone Meister
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stevem wrote on Fri, 03 October 2014 08:35
It would seem that Bill is looking at rev 2 of that 703 board.


I believe my board is a first revision (KEI-1) and that I'm working from the right schematic.

Looks like Bill is absolutely right and that I have reversed every one of the new transistors. Looking at the flat spots on both types of NPN and the PNP, all the old transistors are oriented CBE and the new 2N4001 and 2N4003 are both oriented EBC. Apparently I misinterpreted the datasheets.

Can someone double-check that Zener one more time for correct orientation?



http://i871.photobucket.com/albums/ab276/ResidentToneMeister/Transistororientation_zps4633b33a.jpg~original

[Updated on: Fri, 03 October 2014 12:10]

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Re: Kustom 200 B1 blowing fuses [message #21628 is a reply to message #21094] Fri, 03 October 2014 14:13 Go to previous messageGo to next message
Tone Meister is currently offline  Tone Meister
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Got all the 2N4001 and 2N4003 transistors installed correctly, I believe.

Now the dawgone 1N3754 (CR702) has broken the leads right at the body. I plan to replace it with a 2N3440 (TO-39 case) using the BE junction and snapping the body into the original chassis clip. Does anyone see a problem with that? Here is the datasheet.



http://i871.photobucket.com/albums/ab276/ResidentToneMeister/2N3440_zps0ca477c1.jpg~original
Re: Kustom 200 B1 blowing fuses [message #21629 is a reply to message #21094] Fri, 03 October 2014 15:18 Go to previous messageGo to next message
stevem is currently offline  stevem
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With those factory Type 2n3638 round case transistors when you hold them leads up and with the lead gap facing away from you the configuration from right to left is EBC.
In regards to the 6.2 volt diode, it appears it's in correct .

Also the schematic you posted that you are working from does not show that new cap that you have across that diode?

[Updated on: Fri, 03 October 2014 15:25]

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Re: Kustom 200 B1 blowing fuses [message #21631 is a reply to message #21629] Fri, 03 October 2014 15:37 Go to previous messageGo to next message
chicagobill
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If you hold one of the plastic cased TO-whatever with the legs down and the base is closest to you, then it is ebc. The legs are in a triangular pattern.

Be sure to retest all of your new transistors before reinstalling them.

Edit: I just saw your post about the compensation diode replacement idea. I guess it would work. I just use a 1N4148.

[Updated on: Fri, 03 October 2014 15:47]

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Re: Kustom 200 B1 blowing fuses [message #21632 is a reply to message #21094] Fri, 03 October 2014 15:47 Go to previous messageGo to next message
Tone Meister is currently offline  Tone Meister
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Bill said the leg closest to the flat spot is the emitter, so that drawing above depicts that. In observing that orientation, every one of mine were installed with B and E reversed.

I've wired in the 2N3440 for the 1N3754 and am about to fire up the amp on the limiter.

That cap across that diode replaced a tantalum of the same value that was there before. There are actually separate holes there for the cap and the diode.
Re: Kustom 200 B1 blowing fuses [message #21634 is a reply to message #21094] Fri, 03 October 2014 16:27 Go to previous messageGo to next message
Tone Meister is currently offline  Tone Meister
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OK, There is now 7.4V DC at the RED wire and -7.5V DC at the green wire and that voltage is getting to the preamp. Voltages at Q1-Q4 are good. Still very low output with either channel through a known good speaker. Measured 0.00V DC at the speaker jack.

660mV DC at the anode and 15mV DC at cathode of the 2N3440 that I installed in place of the 1N3754.
Re: Kustom 200 B1 blowing fuses [message #21636 is a reply to message #21094] Fri, 03 October 2014 17:34 Go to previous messageGo to next message
chicagobill
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Good, you got the low voltage supplies up and running. Having no voltage on the power amp output is a good thing. Now that all of the power supplies are working, you need to find out what sections are working and which ones are not.

If you plug a signal into the monitor jack on the back do you hear it through the speaker? If you take a signal out from the same monitor jack and listen to it through another amp do you hear the output from the preamp?

As a warning, if the amp still has the original two wire power cord, you need to make certain that the two amps (the test amp and the listening amp) are grounded correctly before plugging in the audio cable between the two amps. I use a meter set to read ac volts and put one lead on the ground of the first amp and then the second lead to the ground of the second amp. With both amps plugged in and turned on there should be no voltage reading on the meter. If there is, then change the polarity setting of the power switch on one of the amps to make the voltage go away.

I use a battery powered headphone amp to check the monitor output, so there are no ground problems with that.
Re: Kustom 200 B1 blowing fuses [message #21637 is a reply to message #21094] Fri, 03 October 2014 18:01 Go to previous messageGo to next message
Tone Meister is currently offline  Tone Meister
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Feeding a 1K signal into the input and using my homemade probe into a small amp I am able to get strong output from the preamp (BLUE WIRES) at the power board. Can pick up a very strong signal at the MONITOR output and can pick up strong signal from Q700-Q703, but it starts getting weaker at Q706 and Q707.

Measure 33mV at the cathode of CR702 bias diode

[Updated on: Fri, 03 October 2014 18:01]

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Re: Kustom 200 B1 blowing fuses [message #21638 is a reply to message #21637] Fri, 03 October 2014 18:06 Go to previous messageGo to next message
Tone Meister is currently offline  Tone Meister
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I am using a DC powered amp for probing the circuit using this homemade probe which has a 630V capacitor inside.

http://i871.photobucket.com/albums/ab276/ResidentToneMeister/IMG_1328_zps6dee3029.jpg~original
Re: Kustom 200 B1 blowing fuses [message #21639 is a reply to message #21638] Fri, 03 October 2014 18:34 Go to previous messageGo to next message
Tone Meister is currently offline  Tone Meister
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With a 150mV 1K signal into the MONITOR jack, I get zero output from the speaker. However, with a 50mV 1K signal into the preamp input, I can get a weak signal from the speaker, but I can pick up the signal strong at the MONITOR jack.
Re: Kustom 200 B1 blowing fuses [message #21640 is a reply to message #21094] Fri, 03 October 2014 20:22 Go to previous messageGo to next message
stevem is currently offline  stevem
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I just did a test for you on one of my 200B heads!
When I drive the normal channel with .152 volts @ 1K and show at the amps output into a 4 ohm load 18.95 VRMS ( clipping) the AC signal level I read with my voltmeter at the monitor jack is15.9 volts.

When I drive the monitor jack with that same .152 volt test signal I show at the output 2.62 VRMS into that 4 ohm load.
Re: Kustom 200 B1 blowing fuses [message #21643 is a reply to message #21640] Fri, 03 October 2014 21:23 Go to previous messageGo to next message
chicagobill
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Nice numbers Steve.

Now we know that the problem is in the power amp. Q706 and Q707 are the protection circuit transistors don't look for the signal there. Better to look at the drivers Q704, 705, 709 and 709.

If the signal is strong at the collector of Q703, then see what happens at the bases and collectors of Q704-709. Oh and nice signal tracer probe.
Re: Kustom 200 B1 blowing fuses [message #21650 is a reply to message #21094] Sat, 04 October 2014 11:57 Go to previous messageGo to next message
Tone Meister is currently offline  Tone Meister
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Yes, thanks for those numbers Steve. I'll use those for comparison once I get this power section sorted out. I'm gonna poke around and take some readings as Bill directed and will report back. I would love to get this sorted out this morning.
Re: Kustom 200 B1 blowing fuses [message #21651 is a reply to message #21094] Sat, 04 October 2014 12:09 Go to previous messageGo to next message
Tone Meister is currently offline  Tone Meister
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The signal is VERY strong at the collector, emitter, AND base of Q703. Signal is very weak at bases and collectors for Q704, Q708 and Q705, Q709. I tested for that signal at the appropriate RED, BLUE, and YELLOW wires at Q1-Q4 connectors.
Re: Kustom 200 B1 blowing fuses [message #21662 is a reply to message #21094] Mon, 06 October 2014 19:23 Go to previous messageGo to next message
Tone Meister is currently offline  Tone Meister
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Any ideas? Picking up strong signal at Q703 EB and C but it gets weak after that.
Re: Kustom 200 B1 blowing fuses [message #21663 is a reply to message #21094] Tue, 07 October 2014 07:04 Go to previous messageGo to next message
stevem is currently offline  stevem
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I may have some time to dive into one of my amps tonight and probe around for you !
Re: Kustom 200 B1 blowing fuses [message #21665 is a reply to message #21094] Tue, 07 October 2014 07:38 Go to previous messageGo to next message
Tone Meister is currently offline  Tone Meister
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Thanks Steve. Don't know where to proceed from here.
Re: Kustom 200 B1 blowing fuses [message #21667 is a reply to message #21094] Tue, 07 October 2014 12:45 Go to previous messageGo to next message
chicagobill
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Q703 is the pre-driver, after that the the signal goes to Q705 and Q704. It can be that the signal path is broken or that the driver transistors are dead or are not turning on. Odds are against all four drivers being dead, so I'd look to see if the signal is getting to Q705.

Check R718 is it 470 ohms? Is there continuity from the resistor to both the collector of Q703 and to the base of Q705?

Next start taking voltage readings on the driver transistors. The schematic shows that Q705 should have -.7 vdc on the base, -.1 on the emitter and probably -38 volts on the collector. What voltages do you get? What are the voltages on Q704, Q708 and Q709?

I don't remember what transistors do you have in there for the drivers? Have you tested them with your meter?

[Updated on: Tue, 07 October 2014 12:47]

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Re: Kustom 200 B1 blowing fuses [message #21668 is a reply to message #21094] Wed, 08 October 2014 11:20 Go to previous messageGo to next message
Tone Meister is currently offline  Tone Meister
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Driver transistors are NOS RCA 40409 and 40410. Pulled all driver transistors and all test good out of circuit

Q704, Q708 = 40409 (NPN)
Q705, Q709 = 40410 (PNP)

R718, R719, and R702 were out of spec enough so I changed all this morning.

Confirmed continuity from R718 to C of Q703
Confirmed continuity from R718 to B of Q705

VOLTAGES

Q704_________________Q708 <-------- (RCA 40409 NPN)
B = 1.9V______________B = 1.9V
E = 1.4V______________E = 1.4V
C = 40.0V_____________C = 40.0V

Q705_________________Q709 <---------(RCA 40410 PNP)
B = -0.06V____________B = -0.05V
E = +0.05_____________E = +.05V
C = -39.4V____________C = -39.4V

Re: Kustom 200 B1 blowing fuses [message #21669 is a reply to message #21094] Wed, 08 October 2014 13:06 Go to previous messageGo to next message
chicagobill
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For some reason the voltages on Q705 and Q709 are off and I'm trying to figure out why. Do you have the protection circuits Q706 and Q707 hooked up right now? Did you replace these two transistors?

Right now, I guess most important is the circuit around Q707. Did you test/replace diode CR704?
Re: Kustom 200 B1 blowing fuses [message #21671 is a reply to message #21094] Wed, 08 October 2014 14:42 Go to previous messageGo to next message
Tone Meister is currently offline  Tone Meister
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I did not replace Q706, CR703 or Q707, CR704. Just tested CR703, CR704 diodes again and they test fine (in circuit).

Pulled Q706 and Q707 and tested them just now. Q707 (2N3638) tests fine, but Q706 (2N3567) is open from B-E. Gonna swap in a 2N4401 and see what we have.

[Updated on: Wed, 08 October 2014 14:42]

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Re: Kustom 200 B1 blowing fuses [message #21672 is a reply to message #21094] Wed, 08 October 2014 16:32 Go to previous messageGo to next message
Tone Meister is currently offline  Tone Meister
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OK, subbed in a 2N4401 at Q706 and no change in signal strength.
Re: Kustom 200 B1 blowing fuses [message #21676 is a reply to message #21094] Wed, 08 October 2014 17:54 Go to previous messageGo to next message
chicagobill
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You have replaced all of the diodes CR700-CR701-CR702. CR702 is a transistor and the other two are what diodes? Try replacing the transistor with a generic 1N4148 diode.
Re: Kustom 200 B1 blowing fuses [message #21677 is a reply to message #21676] Wed, 08 October 2014 19:16 Go to previous messageGo to next message
Tone Meister is currently offline  Tone Meister
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chicagobill wrote on Wed, 08 October 2014 17:54
You have replaced all of the diodes CR700-CR701-CR702. CR702 is a transistor and the other two are what diodes? Try replacing the transistor with a generic 1N4148 diode.


Yes, I have replaced CR700, CR701, and *CR702. The schematic calls *CR702 a diode, but what the hey. I only have 1N4448 here and will make the swap and see what happens.
Re: Kustom 200 B1 blowing fuses [message #21678 is a reply to message #21094] Wed, 08 October 2014 19:46 Go to previous messageGo to next message
Tone Meister is currently offline  Tone Meister
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Good call on CR702, Bill. Replaced the 2N3440 with a 1N4448 and she's up to full power now. So, apparently subbing in a 2N3440 (B-E junction) for the 1N3754 is not the way to go.
Re: Kustom 200 B1 blowing fuses [message #21679 is a reply to message #21094] Wed, 08 October 2014 20:56 Go to previous messageGo to next message
chicagobill
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Great news! And I bet that the voltages on the drivers are back to normal too.

I started to experiment with mounting 1N4148 diodes into short pieces of aluminium tubing as replacements for those temperature compensating diodes. I never got around to heat testing them in circuit though. Maybe this Fall that can be one of my to dos.

Anyway, glad to hear that it's back up to volume again.
Re: Kustom 200 B1 blowing fuses [message #21680 is a reply to message #21094] Wed, 08 October 2014 21:14 Go to previous messageGo to next message
Tone Meister is currently offline  Tone Meister
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Yeah, and thanks Bill and Steve for your help and patience. This amp likely took a lightning strike or was run on an inferior generator at some point in its life. It had been sitting for 15 years or more in my friend's basement, so who knows.

Thanks guys!
Re: Kustom 200 B1 blowing fuses [message #21681 is a reply to message #21094] Thu, 09 October 2014 06:18 Go to previous messageGo to next message
stevem is currently offline  stevem
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That's great news and pat yourself on the back for stickin with it!

On all of my amps , Kustom or not I place a 130 MOV across the AC line input just in case the over volt potential nightmare takes place !
Re: Kustom 200 B1 blowing fuses [message #21690 is a reply to message #21614] Sat, 11 October 2014 02:28 Go to previous messageGo to next message
Kustom_Bart is currently offline  Kustom_Bart
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Don, open an account at photobucket.com and you can upload pics (just one or multiple at a time)right from your computer to your photobucket account, then it will give you different options for links to use, ie hold your mouse over the pic you want to share and it will bring up a little gear looking icon, it will bring up a drop down menu and click on "Share links" then it gives you 4 different options of link types. The bottom link is the one you want for forums, when you click the link, it automatically copies it , come to your post and right click and click paste and you are done and submit your post. You will have your pic in your post. If you want multiple pics, do it multiple times. Smile


This should be made a sticky post in a HOW TO Section of the forum.

[Updated on: Sat, 11 October 2014 02:39]

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Re: Kustom 200 B1 blowing fuses [message #21742 is a reply to message #21094] Sat, 18 October 2014 10:04 Go to previous messageGo to next message
Tone Meister is currently offline  Tone Meister
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My buddy picked up his 200 B1 a few days ago and called me yesterday with a report. He wasn't specific about the speaker cab and speakers he's using, but said the amp sounds great with a Strat. But he went on to rave about the tone with an SG plugged in. Instant John Fogerty - CCR tones and very quiet!

Many thanks to Bill and Steve for their patience in helping me sort out the multitude of small problems I encountered in the amp. Basically, it was a complete circuit restoration and the end result exceeded expectations.

-Stan
Re: Kustom 200 B1 blowing fuses [message #21744 is a reply to message #21094] Sat, 18 October 2014 17:54 Go to previous message
stevem is currently offline  stevem
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Great to hear!
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