Author Topic: Repairing a Pride of Texas  (Read 536 times)

Max

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Repairing a Pride of Texas
« on: April 04, 2020, 05:07:18 AM »
I just put my hands on a broken Danelectro Pride of Texas. Honestly, I was hoping for something easier to repair. Damn it, this thing is all smd, also tracing it (  ;) ) will be a nightmare. However, it looks like the problem is on the switching board, so hopefully it is the relay that's faulty.
More to come when I have time to work on it...
PS: according to a couple of stickers on the box (that were casually covered by some white labels...) this was already on offer on Amazon as reconditioned.

EDIT: I just realised that probably I picked the wrong forum for this thread, if anyone reckons appropriate to move it somewhere else please go ahead.
« Last Edit: April 04, 2020, 02:21:23 PM by Max »

Max

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Re: Repairing a Pride of Texas
« Reply #1 on: April 06, 2020, 05:48:18 AM »
Update 1: I checked the switching board, the resistance across the relay's solenoid looks fine, but I can't read any voltage when pressing the foot-switch. It's a latching relay, so I expect a voltage only when the foot-switch is activated, +5V set and -5V reset. On the other hand, also applying 5V directly to the solenoid doesn't have any effect, so I'm a bit puzzled.
There is a strange IC on the switching board, I can't find any information on the internet. It reads F1102AMB 1741N, any idea?

This is going to be tricky...
 :(

aion

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Re: Repairing a Pride of Texas
« Reply #2 on: April 06, 2020, 08:05:16 AM »
The bypass uses a latching relay driven by a microcontroller, not dissimilar from the AMZ or Jack Deville type. The F1102AMB IC is the microcontroller. When the footswitch is pressed, the IC sends a brief pulse to trigger the relay. You'd need a scope to see whether it's sending it properly or not though - it's only a few milliseconds long.

You could replace the whole switching arrangement with a 3PDT switch - the relay is doing essentially the same thing. You'd just need to trace out the wires to find what corresponds to what. Other than the LED, it's all on the I/O board if memory serves.
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Max

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Re: Repairing a Pride of Texas
« Reply #3 on: April 06, 2020, 10:02:05 AM »
Thanks, that makes sense, I'll check with my scope. So it's still possible that the relay is the culprit.
Actually, it wouldn't be difficult to replace it with a 3pdt, if it weren't for the space inside the enclosure. I'll check, but it doesn't look high enough for a mechanical switch.

Max

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Re: Repairing a Pride of Texas
« Reply #4 on: April 08, 2020, 08:11:13 AM »
Bad news, maybe it's fault of my cheap scope, but I can't see any signal on the solenoid's pins.
I can try and troubleshoot the switching board, but it would be definitely easier to replace it with something like the nope relay bypass.
I may also design a new pcb to replace the original one.
Mmmh, need to mull it over  :-\ :-\
EDIT: of course I couldn't see anything, the +V on the DC input is short to GND  :o :o
Now, with all the smd parts good luck to me in finding where the short is... I need to identify the reverse voltage protection diode.
« Last Edit: April 11, 2020, 03:31:40 AM by Max »

Max

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Re: Repairing a Pride of Texas
« Reply #5 on: April 12, 2020, 05:53:04 AM »
Easter update: I (carefully) removed the reverse polarity protection diode and separated the two boards. Well, the diode is fine and the short is still there, so I traced the whole board and found two possible places for a short, the 7550 voltage regulator and the zener Z1. Hope it's the zener...
Anyway, here's the schematic. I still have a big ? about the microprocessor, I couldn't find any information online, but the pins' function is pretty obvious, now. Also the capacitors (except for the electrolytics) will have to be guessed, though I expect the usual suspects.
I think I'll try to power up the effect board alone to see if that works.
« Last Edit: April 24, 2020, 07:36:09 AM by Max »

Max

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Re: Repairing a Pride of Texas
« Reply #6 on: April 17, 2020, 07:19:10 AM »
Third (!? maybe) update and advice request.
I found the culprit: it's the zener marked as Z1 and shown in the picture below. Once removed everything works like a charm  8)
First I tried to power the effect board on it's own, just to realise that part of the in-out circuitry is in the switching board, so I built a veroboard with the same parts I was lucky enough to have lying around and found that the effect works perfectly. Then I went on and removed Z1 from the switching board, and found it is shorted in both directions.
Now, the circuit works perfectly without Z1, would you suggest to leave it out or look for a replacement?
Consider that:
a) I have no idea of what kind of zener that is, and is bigger (in size) than anything I've found so far.
b) I'll most likely sell the effect

« Last Edit: April 24, 2020, 07:37:08 AM by Max »

aion

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Re: Repairing a Pride of Texas
« Reply #7 on: April 17, 2020, 07:35:36 AM »
The zener is a 1N4742 (12V) that is just used for overvoltage protection for the TC1044 charge pump. So likely someone powered it with 18V or something and it fried the zener (which means it did its job!). It's not strictly necessary to the circuit but it will of course be susceptible to overvoltage without it.
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Max

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Re: Repairing a Pride of Texas
« Reply #8 on: April 17, 2020, 10:04:16 AM »
Great, perfect, thank you very much, now I can try to find it somewhere (hopefully I won't have to buy a bunch of 10 or 100).
So this topic is heading toward a happy ending (thanks to aion  ;) )

Cheers,
Max.

FuzzMonkey

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Re: Repairing a Pride of Texas
« Reply #9 on: April 25, 2020, 11:43:05 PM »
I've been bringing an MXR EVH Phase 90 back from the dead. The PCB itself uses a combination of SMD and through-hole components and I've had a much easier time replacing the SMD components (two op-amps, the TL072 used as the buffer and LFO and the TLC2264 used for the 4 phase shifting stages) than the through-hole components (the reverse-polity protection diode and the 5.1-volt Zener diode).

So I've quickly learnt not to fear SMD components.

Max

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Re: Repairing a Pride of Texas
« Reply #10 on: April 26, 2020, 01:29:14 AM »
Yep, they are scary as hell at first, but after a while I'm starting to like them. After the Orange MkII circuit I'm drawing all my jfet based boards with smds. OK, it started out of necessity, but now it's making things more interesting.

FuzzMonkey

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Re: Repairing a Pride of Texas
« Reply #11 on: April 26, 2020, 05:21:10 PM »
My hands were shaking when I was trying to position the op amps not to mention soldering them. You'd get everything lined up perfectly on the pads and then bump it when attempting to solder it.

I should get some soldering paste, that would probably help hold things in position until you get both ends tacked down.

Max

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Re: Repairing a Pride of Texas
« Reply #12 on: June 27, 2020, 03:26:34 AM »
Et voilą, it took me two months to get the replacement diode from China, but there you go, it works!
Many thanks to Aion for the help ;)