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autoprod
Copper Member
Norway
11 Posts |
 Posted - 01/16/2009 : 16:37:52
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Ah - Sorry to start off with what seems well documented -
This DD2 was trashed after a power reversal - so of course I snagged it and replaced Zener D6. Some traces were cut from the heat, and I bridged those. Now it sounds like it should when the pedal is pressed, but the LED does not come on except in "hold" mode - Also, it does not latch, but reverts to bypassed mode as soon as the swith is released.
The 5v regulator reads fine (IC10) - likewise the caps c49 + c51, and resistors R57 + R59. Will I have to scrounge for a BA634?
Any and all hints appreciated,
-SJ
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Edited by - autoprod on 04/03/2009 01:01:21 |
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DeFrag
Moderator
USA
3409 Posts |
Posted - 01/16/2009 : 17:23:55
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Welcome to Bossarea autoprod! 
One of our resident techs should be around shortly. |
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autoprod
Copper Member
Norway
11 Posts |
Posted - 01/17/2009 : 14:40:38
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Great - and thanks. I'll be replacing elecrolytes in the meantime.
Glad I found this place. Should come in handy. |
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autoprod
Copper Member
Norway
11 Posts |
Posted - 01/17/2009 : 19:48:20
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| Another tiny hint - It now no longer engages the effect when the pedal is pressed down - it only does so in the "hold" setting - and it only repeats the first milliseconds of the signal. If one holds down the pedal while switching to another mode, the various settings work for a short while, then slowly grows weaker and eventually dies out. |
Edited by - autoprod on 01/17/2009 21:36:23 |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 01/21/2009 : 14:37:14
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Hi autoprod
Apologies for not replying earlier,
I needed to think about this.
First of all Welcome to the forum from Australia.
You may have noticed, that there are about (8) or more repairs,
running simultaneously on the forum at the moment.
And we all do this in our spare time (late at night), & the willingness to help others out.
Now lets pull up our shirt sleeves, & put on our propeller-top thinking-hats. 
I have been reading your post, & thinking about it, while at work today.
I guess you know, I'm going to ask you for some closeup pictures of the affected area that you repaired?
Did you replace D6 with a 11V or 12V 1 watt zener?
Was the faulty zener short circuit, or open circuit,
it does make a difference, when trying to diagnose the fault.
Do you know how hard a rev voltage belting the DD-2 got?
Was it just 9V rev, or was it more like 12V unregulated rev. volts?
As you know the higher voltage rev. volts would do more damage.
Are you 100% sure, you repaired the damaged traces on the PCB.
Is your Schematic off the web (freeinfo), or is it an actual Service sheet?
Your post indicates that you already have the DD-2 Schematic.
Just so we are looking at the same paperwork.
The Time-Delay-Hold switch, is controlled by a few transistors & diodes.
My suggestions are to to check (in schematic order).
Q13 - Q12 - Q11
D13 - D5 - D7 - D12 - D11 - D9
These all form part of the Delay switch function.
And all the wires/ribbon to the switch.
I guess you are aware, that the long chip DIL DD-2 & DD-3,
have a power on self test delay, before they work it's about 3 to 5 seconds,
it catches almost everyone out, thinking that the pedal is faulty.
Yes it even caught me out late one, when I was very tired. 
Are you able to check the operation of IC9 the BA634?
I don't think it's faulty, depending on if D6 went open or shorted.
Shorted would be much better, as it would have protected the rest of the circuit.
How bad were the electro. caps around the D6 & the 78L05 reg?
Are any parts getting hot, when you touch them?
Perhaps the 78L05 is slightly damaged, & the 5V rail is clamping.
Are you able to test this, while it's running?
Solder a couple of short pieces of wire to the output of the 5V regulator & gnd, connect them to your multimenter, & watch the 5V rail?
Use a PSA, or 9V DC regulated supply.
If you are running a slightly higher voltage into the 5V reg, it will have to dissipate the extra volts as heat, & might be going into thermal shut down,
I'm just thinking-typing out loud here.
Do you have any test gear, like a signal generator, oscillator & a Scope, & some probes?
Let me know how you get on.
Now I have to go & look at my ODB-3 & schematic.
Laurie asked me to help him out, his head was starting to hurt  .
I gather you might know how difficult it can be to do remote diagnosis & repair to electronic equipment?
Please double check the burnt, damaged areas of your PCB.
Send us some pictures.
Good luck
Regards Dr. Bob
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Edited by - Dr. Bob on 01/21/2009 14:47:21 |
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autoprod
Copper Member
Norway
11 Posts |
Posted - 01/25/2009 : 19:55:26
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Thanks for the welcome, and the suggestions.
I used a 10 V/1 Watt Zener (1n4740a) - the original diode is missing in action. There had been quite some heat going on, since the two neghbouring traces also had melted. The box did not work with the diode removed.
I presume the reverse voltage was at 9 volts - the box was given me as trash. I assume the power was left on for a while though, seeing that it came off a rather largish pedal board.
The electro. caps around the D6 & the 78L05 reg measured just fine and showed no signs of stress. I replaced the caps anyhow, just in case.. Both 9 and 5 volts test points read up good, with battery and 9 V supply. No parts seems to get hot.
I'll be back shortly with pictures.
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 01/26/2009 : 07:09:56
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quote:
Originally posted by autoprod
Thanks for the welcome, and the suggestions.
I used a 10 V/1 Watt Zener (1n4740a) - the original diode is missing in action. There had been quite some heat going on, since the two neghbouring traces also had melted. The box did not work with the diode removed.
I presume the reverse voltage was at 9 volts - the box was given me as trash. I assume the power was left on for a while though, seeing that it came off a rather largish pedal board.
The electro. caps around the D6 & the 78L05 reg measured just fine and showed no signs of stress. I replaced the caps anyhow, just in case.. Both 9 and 5 volts test points read up good, with battery and 9 V supply. No parts seems to get hot.
I'll be back shortly with pictures.
Hi autoprod
That is strange, as the unit should have worked properly with the Zener out of circuit.
The Zener is across the rail & not in series with it.
With the Zener out of circuit, the unit should work properly, but be very careful as there will be no rev. voltage protection.
I would go back to the Zener & burned-damaged tracks.
If you have to, remove the zener, with all the above cautions.
See if you can get the pedal to work with it out of circuit.
Then replace it.
It's also best to use an 11V 1W zener, if you can locate one.
I'm guessing that you may shave missed a damaged track or link to another component.
Regards Dr. Bob
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autoprod
Copper Member
Norway
11 Posts |
Posted - 01/30/2009 : 00:44:10
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While waiting for the camera to charge - here's a report on progress:
Checked D5, D7, D8, D9, D11, D12, D13 out of circuit - All OK
Checked Q5 and Q8 by swap/remove - seems OK
Checked C6, C23, C49, C50, C51, C55 out of circuit - All OK
Is there any quick and common replacement for the 2SC2603 (F) and 2SA1115 transistors? Would a general NPN and PNP work? Such as a set of 2N3904 and 2N3906's ? |
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autoprod
Copper Member
Norway
11 Posts |
Posted - 03/02/2009 : 02:47:00
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Here's an image of the reconsctructed paths. Looks ugly, but reads ok. The board had no other visible strains or faults.
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autoprod
Copper Member
Norway
11 Posts |
Posted - 04/03/2009 : 01:02:56
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Finally:
- Replaced D3 (500mA 5.1 volt Zener)
- Replaced BA634
..and it works again. |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 04/03/2009 : 11:02:47
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quote:
Originally posted by autoprod
Finally:
- Replaced D3 (500mA 5.1 volt Zener)
- Replaced BA634
..and it works again.
Hi autoprod
Thanks very much for the update.
Another vintage DD-2, save from becoming landfill...
Was D3 (zener) actually damaged, open-shorted?
I recently had a DD-3 long chip, dropped off on my lab bench.
It belongs to my good friend Justin,
it appears to be exhibiting the same fault condition/s.
I have it apart, but need some "free" time to look at it more closely.
Regards Dr. Bob |
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autoprod
Copper Member
Norway
11 Posts |
Posted - 04/03/2009 : 12:56:15
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Actually, I replaced both of these at the same go - so D3 could be fine for all I know. I just wanted to make sure.
I got the BA634 from http://www.vintageplanet.nl/ |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 04/03/2009 : 17:54:03
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Thanks autoprod
Here is an older lnk from 2007 on a similar DD-3 fault,
that wasn't resolved.
http://www.bossarea.com/forum/topic.asp?TOPIC_ID=2558
Do you have a datasheet for the BA634?
My quick search of familiar sites, came up empty handed.
Regards Dr. Bob |
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autoprod
Copper Member
Norway
11 Posts |
Posted - 04/05/2009 : 22:52:04
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| Couldn't find a datasheet on it myself. But found out that it's used in my Arps as well, so I stocked up on a few for future repairs. |
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Topic |
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DD-2 not latching (RESOLVED)
