Kustom Sidewinder [message #13417] |
Mon, 19 April 2010 01:03 |
Goonak
Messages: 19 Registered: April 2010
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Junior Member |
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Hello - can anyone direct me to the correct reverb tank for the Kustom Sidewinder please? There is an Accutronics tank that came with the amp when I bought it about 5 years ago, but I'm not sure it's the right one. The number is 4FB2A5C. The reverb has never worked on this Sidewinder amp since I've had it.
BTW, I also have a Kustom 150 and a 250, and both of those amp heads have Gibbs tanks in them and work fine. I'm hoping that maybe there's just the wrong tank in the Sidewinder?
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Re: Kustom Sidewinder [message #13425 is a reply to message #13417] |
Mon, 19 April 2010 12:12 |
chicagobill
Messages: 2006 Registered: April 2003
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Senior Member |
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Welcome!
According to the schematic, the Sidewinder uses the same effects board as the 150 and 250 metal fronts, PC5068. So they will use the same tank, Kustom part #031-0047-00.
Maybe one of the other guys here has the tank codes handy, but if they don't, I'll dig up the correct Accutronics code number for the tank. The tank you have is not original and has a grounded input jack.
The correct tank should have an isolated input jack and a grounded output jack, so the 5th letter in the tank code should be "C" and not "A".
Hope this helps.
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Re: Kustom Sidewinder [message #13442 is a reply to message #13417] |
Tue, 20 April 2010 11:55 |
chicagobill
Messages: 2006 Registered: April 2003
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Senior Member |
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That's quite a mod there. I guess the original power amp died and rather than rebuild it, someone decided to replace it.
In order to restore it, you would need a power amp PC board, an aluminum channel for mounting the output transistors and a thermal cut off switch. Unfortunately the only place you will get these items is from another Kustom amp.
Kustom used a modular approach to building these amps, so the power amp board in your amp is the same as in a 150 metal front as well as a few others. You may be able to find a donor head out there and steal the parts that you need.
As for the original question, the correct tank for your amp is an Accutronics 4BB2C1D. If you still get no reverb with the correct tank, then do as Steve mentioned and see some of the other posts to find out if the problem lies in the drive or the return side of the amp.
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Re: Kustom Sidewinder [message #13447 is a reply to message #13417] |
Wed, 21 April 2010 11:51 |
chicagobill
Messages: 2006 Registered: April 2003
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Senior Member |
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Either one of those tanks will work for you. Antique Electronics is having a sale right now and the tank is selling for $17 right now.
If you go to the Accutronics site, there is page of code numbers that will explain the different parts of the coding system. The two most important parts of the code for any Kustom amp is the input impedance and whether or not the RCA jacks are both grounded or not.
Kustom used a number of different tanks through the years for different eras and models. The main difference was in the input jack grounding. For example a K100B or K200B series amp must have a grounded input and output jack or it will not work at all. While on a 150 or 250 metal front the input jack must not be grounded for it to work. Your amp needs an ungrounded input which is designated by the 5th digit "C", so either one of the two you have found will work correctly.
The other differences in the two tanks, is in how long the delay is and how it was designed to be mounted.
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Re: Kustom Sidewinder [message #13449 is a reply to message #13417] |
Wed, 21 April 2010 13:25 |
chicagobill
Messages: 2006 Registered: April 2003
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Senior Member |
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The fastest test for your reverb is to take the RCA cable that connects to the tank and touch the tip of each connector with the amp on and the reverb control turned up. One is the send side, and the other is the return. Touching the return cable tip should cause a loud buzz in the amp that is controlled by the reverb controls on the amp.
If you hear the buzz, your return circuit is working, and the problem is in the drive side. If you don't hear the buzz, then the return circuit needs repair.
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Re: Kustom Sidewinder [message #13454 is a reply to message #13417] |
Thu, 22 April 2010 10:01 |
chicagobill
Messages: 2006 Registered: April 2003
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Senior Member |
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You could try testing it by taking a cable from the send jack and plugging it into the input of another amp.
If you do this be certain that the two amps are grounded exactly the same before connecting the wire, as there is a slight chance of causing damage to the amps if the grounds are mis-wired. The safest choice would be a small battery operated amp or a headphone amp.
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Re: Kustom Sidewinder [message #13465 is a reply to message #13463] |
Mon, 26 April 2010 12:02 |
chicagobill
Messages: 2006 Registered: April 2003
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Senior Member |
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Goonak wrote on Sat, 24 April 2010 23:54 | ...the black wire was left hanging. Could this have something to do with the reverb not working?
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It might, but I'd doubt it. If the board was not grounded there would be no signal at all going through the amp. The black wire is the ground connection for the original power amp. Let me ask this, does the trem/vib work on the amp?
The reverb send is driven by one half of IC3, a very common dual opamp. The only thing between the chip and the tank are a couple of resistors and the cables. Did you check the cables for continuity and for shorts? Use your meter and check resistors R11, R12 and R13. Also check to be sure that there are no bad solder joints or bridges on the PC board.
If all of this checks out, the only other thing to try is to replace the chip. Almost any dual opamp will work in this circuit, how are your soldering skills?
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Re: Kustom Sidewinder [message #13469 is a reply to message #13465] |
Tue, 27 April 2010 00:36 |
Goonak
Messages: 19 Registered: April 2010
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Junior Member |
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OK, well first off, I did connect the black wire (#2) to ground and nothing major happened. Still no reverb.
Yes, the trem/vib does work on the amp.
The reverb cables are good, continuity checks out. Solder joints look OK, no bridges, and R11, R12 and R13 check out OK too. But what about C8? Could that be an issue?
Also, the more I look at the board the more I'm convinced that IC3 has been changed out once before. The solder connections are not as clean as the IC6 that's on the board. Plus there are scratches between the pinouts for IC3, so someone was trying to clean up the area previously.
There's an LM1458 currently installed for IC3. I may have an extra one of those around. If not, I can get one. My soldering skills are pretty good. I've repaired and built some effects pedals, just never worked on an amp before.
Anyway, pinout 7 on IC3 powers the reverb "send" correct? I can change out this op amp like you suggest, but before I do, can't I test whether or not both halves of the currect 1458 are working right? How would I test pinout 7?
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Re: Kustom Sidewinder [message #13471 is a reply to message #13417] |
Tue, 27 April 2010 06:04 |
stevem
Messages: 4773 Registered: June 2004 Location: NY
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Senior Member |
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If there is a radio shack near by I would pick up an IC socket and solder it in so that it is the last time you have to touch a iron to that circuit board in that area and then try out the new IC chip.
Unless C8 is a ceraimic disc type type cap ( not one of the orange or blue ones) I dought its bad, but pulling out whatever cap is used to check it for a short might be worth the effort anyway.
If you can scan and email, or fax me that boards schematic I can tell you if a 1458 chip is a good sub for the original.
Steven.Magnotti@avispl.com
fax 914 662 3735
[Updated on: Tue, 27 April 2010 06:04] Report message to a moderator
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Re: Kustom Sidewinder [message #13474 is a reply to message #13417] |
Tue, 27 April 2010 11:52 |
chicagobill
Messages: 2006 Registered: April 2003
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Senior Member |
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First off, if you look at the board there is a metal bracket that the pots mount through. This bracket is soldered to the ground trace on the PC board. So when the board is mounted to the chassis, the ground circuit is complete. The black wire actually grounds the original power amp board to the front panel, eliminating a potential ground loop.
Yes, C8 is involved in the send to the tank, but as it parallels R13, which takes most of the load, it really only adds a bit more high frequency to the signal going to the tank. Test it to be thorough. In looking at the schematic the input cap C6 and resistor R10 should be checked as well.
Well, you know that at least one half of the chip is ok as it functions as the output buffer for the FX board. Test IC3 by reading the voltages on the pins. There should be +12 volts dc on pin 8 and -12 volts dc on pin 4. There should be nearly 0 volts on all of the other pins. If there are a few mVs on any of the pins, that's ok. That being said, even if the voltages read ok there may still be a problem with the chip.
This circuit design places the tank in the feedback loop of the driver chip, so neither side of the input coil is grounded. Your amp came with the wrong tank which would have grounded the output of the chip, which may have caused it to fail. This is pure speculation on my part, but it is something to look into.
Steve's suggestion of adding a socket is fine, as that will make any later chip replacement a snap. The original IC was a 5558, which is basically the same as the 1458 chip that is in there.
Steve: This amp uses a PC5068 FX board just like what's in a metal front series head. If you don't have a copy of the schematic, let me know, and I'll email one to you.
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Re: Kustom Sidewinder [message #13507 is a reply to message #13417] |
Fri, 30 April 2010 12:45 |
chicagobill
Messages: 2006 Registered: April 2003
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Senior Member |
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Great to hear of your progress!
The two caps C16 and C26 are compensation caps for the uA739 chip. If the preamp is working, I wouldn't worry about replacing them.
Is the chip the original 739 or has it been replaced with a 4739 chip? The newer 4739 didn't need the external compensation parts that the original 739 did.
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