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Projects => General Questions => Topic started by: Vivek_rc on September 06, 2020, 03:21:19 AM

Title: Dandy Horse - no output
Post by: Vivek_rc on September 06, 2020, 03:21:19 AM
Hi All,

I had just powered up my Dandy horse and it was going well, was able to bias and got a nice flange. All going good, had it running in the blend mode and then suddenly there was a lot of static. And now my effected signal has no output and only get the dry signal when I flip the blend switch. I checked everything, voltages all look good and I followed the biasing steps again, clock frequency is set correctly. But now I donít hear a signal on test Pad 6. I do hear a signal in test Pad 5. Iím connected SW1 and testing on a test box. So weird that it was working nicely and then boom...any help and advice would be appreciated

(https://uploads.tapatalk-cdn.com/20200906/815efcde8f5a6c0f39011067abab2a5f.jpg)
(https://uploads.tapatalk-cdn.com/20200906/023f005e4467f9bba369c197bf251e9a.jpg)

(https://uploads.tapatalk-cdn.com/20200906/bce20d41011d4dde25bc9fe4131675cb.jpg)



Sent from my iPhone using Tapatalk

Thanks
Title: Re: Dandy Horse - no output
Post by: Vivek_rc on September 06, 2020, 04:09:04 AM
I audio probed and Iíve narrowed it down to around IC2.2, I donít get any output from pin 10,11. Going into IC2.2 I can hear the effected signal on pin 15/14, but no output on  pin 11/10. I tried swapping the v571 I had on the aqua boy build and same outcome, no signal and no output on test pad 6. Chip itself is good and it works in the aqua boy. I also wired up the 3pdt switch just to rule that out.

Any advice would be greatly appreciated?


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Title: Re: Dandy Horse - no output
Post by: Scruffie on September 06, 2020, 08:12:27 AM
Voltages por favor.
Title: Re: Dandy Horse - no output
Post by: Vivek_rc on September 06, 2020, 10:05:18 PM
Voltages por favor.
Hi,

Thank you for your help,

These are the voltages Iíve captured. Something doesnít look right on pin 7 of the v571.

(https://uploads.tapatalk-cdn.com/20200907/dfd550ea937fa63d7171b2ea160e7e84.jpg)


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Title: Re: Dandy Horse - no output
Post by: Scruffie on September 07, 2020, 05:07:15 AM
Well you've definitely pin pointed it to the correct area and you've checked it's not the chip so I suppose my only suggestions are to re-flow the solder joints around there and double check the values of R5 & 6.
Title: Re: Dandy Horse - no output
Post by: Vivek_rc on September 07, 2020, 06:49:40 AM
I reflowed the area around IC2 and audio probed again, Checking the flow seems I’m not getting any output on pin 10 and 11 of IC2. I’ve swapped it out with the one I have in the aquaboy and Auquaboy works fine with v571. Also getting the expected voltages out of pin 10 and 11 but just  no audio....
Title: Re: Dandy Horse - no output
Post by: Scruffie on September 07, 2020, 06:55:19 AM
Sorry, I should have read more thoroughly, I was talking about pin 7 of the 571, the voltage shouldn't be that low and that needs taking care of before you worry about output at pin 10.
Title: Re: Dandy Horse - no output
Post by: Vivek_rc on September 07, 2020, 07:04:22 AM
I checked on the PIn 7 low voltage issue and I confirmed R5 and R6 are 47k and also reflowed the area, still getting around 2V on pin7.
Title: Re: Dandy Horse - no output
Post by: Scruffie on September 07, 2020, 07:12:04 AM
What happens to pin 7's voltage if you remove IC1 from the socket? And the same for IC6.
Title: Dandy Horse - no output
Post by: Vivek_rc on September 07, 2020, 07:30:03 AM
Hey, back in business. I reflowed again all the components around ic2 and get a effected output now.. When I remove IC1 the voltage on pin7 is 6.8V. When I insert IC1 the voltage remains at 6.8V. Is that still too low a voltage or would it be ok?
Title: Re: Dandy Horse - no output
Post by: Scruffie on September 07, 2020, 07:44:49 AM
6.8V is just fine :) Congrats on getting it going again.
Title: Re: Dandy Horse - no output
Post by: Vivek_rc on September 07, 2020, 07:48:33 AM
Thanks so much for your Patience, help and support.
Title: Dandy Horse - no output
Post by: Vivek_rc on September 07, 2020, 09:07:21 PM
Hmmm.... seem to be back in the same position, where voltage on Pin 7 drops down to 2V. When I reflow the joints or clean up the solder joints with some alcohol, it starts to work, I get effected output and the voltage on PIN 7 sits around 6.8V, but I notice that as I leave it running the voltage on Pin 7 gradually starts to fall and once it gets down to 2V, just get a lot of static. Still trying to figure this out...? Hmm strange one. Could it be a defective Component around the pin7 region?
Title: Re: Dandy Horse - no output
Post by: Vivek_rc on September 08, 2020, 12:23:00 AM
I replaced c29, c7, c12,r5 and r6 out of frustration and seems to have fixed the issues and flanging again, pin 7 of IC2 is sitting around 6.8V.  Iím leaving it run for a while to see how it fares . I had some weird readings earlier where pin 7 shot up to 14V. I cleaned up the solder side with a toothbrush and alcohol and Seemed to have stabilised now.
Title: Re: Dandy Horse - no output
Post by: Vivek_rc on September 08, 2020, 03:23:00 AM
Coming back to the same situation, it runs ok for a while, all voltages check out but gradually pin 7 on IC2 starts to drop to 2V and then no output, no changes made just running it On flange mode through a looper...
Title: Re: Dandy Horse - no output
Post by: Scruffie on September 08, 2020, 06:36:00 AM
Sorry to hear you're still having trouble! Well it definitely sounds like a cap problem with its cyclic nature... C4 & 6 would be possible suspects to try replacing too, I highly doubt it's related to any film or ceramic caps.

I think I spot some Chang brand caps so am I to assume some of the parts might be from Tayda?
Title: Re: Dandy Horse - no output
Post by: Vivek_rc on September 08, 2020, 06:44:34 AM
I just a minute ago replaced C6, same issue And will try replacing c4 as well and see how it goes. And yes some of the caps are from tayda. I see how I go and maybe get better caps if problem still persists. Hey man thanks a lot for your advice and support, I appreciate it.
Title: Re: Dandy Horse - no output
Post by: Vivek_rc on September 08, 2020, 07:39:57 AM
Iíve replaced both caps and pin7 voltage is really intermittent, sometimes it goes to 6.2v and sometimes it drops to 2V, and sometimes itís just fluctuating Between 2 to 4 V really weird. Iíve left it running and will see in the morning again. Also ordered two more N571 just in case....😕.
Title: Re: Dandy Horse - no output
Post by: jimilee on September 08, 2020, 09:35:08 AM
I would reflow all the sketchy looking solder joints.


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Title: Dandy Horse - no output
Post by: Vivek_rc on September 08, 2020, 06:38:21 PM
Iíve ordered some Panasonic electro capacitors and will replace all the electro caps connected to IC2. Iím also going to replace the IC socket for IC2 just to rule it out. Also got a new NE571 on the way. Although this is frustrating, Iím learning a lot and looking at this as a challenge to get this working. Will report back on how I go in a few days, thanks again for the support Scruffie and Jimilee
Title: Dandy Horse - no output
Post by: Vivek_rc on September 10, 2020, 02:45:59 AM
Hereís the update . I replaced IC2 socket, replaced c4, c6, c7 with Panasonic caps and evening put in a new ne571, same issue, wasnít working. Replaced C27 thinking itís linked to IC2 might help, didnít solve the problem. I put back in original v571.

Was about to throw in the towel. But Scruffies comment on Tayda caps kept ringing in my mind, so on a whim decided to replace C54 and C63, the two 100uf caps, with Panasonic caps. No logic behind it.  And circuit started to work as expected and itís been running now for 3 hours the voltage on pin 7 has remained stable at 7V and getting a modulated output.

Will keep it going for a few more hours and see if any issues come up. Itís only been running in the flanger mode.

Was trying to read up to see how the caps for the voltage regulator could have an effect on the NE571, would be interesting to know.

So should I throw out all my tayda electro caps ? Never had an issue for my other builds until this one....
Title: Re: Dandy Horse - no output
Post by: Vivek_rc on September 10, 2020, 03:50:05 AM
No good, after a few hours Pin 7 is now sitting on 14V and sometimes drops to 7V and then back up to 14V. Iíve got some 22uf electro caps on the way, going to replace all of the caps so there will be no Tayda sources electro caps on the board. Will check in again in a day or so
Title: Re: Dandy Horse - no output
Post by: Scruffie on September 10, 2020, 10:15:02 AM
So should I throw out all my tayda electro caps ? Never had an issue for my other builds until this one....
See, there's the problem with Tayda, 99% of the time, the parts are fine, but that 1% means having to and being able to track down what didn't work.

But honestly, seeing as you replaced all the caps around the compander, I'm a little stumped as to what's going on... It would be logical to expect voltage variation elsewhere in the circuit if it was an electro elsewhere.

I do wonder if taking IC1 & IC6 out of the socket and keeping the test going might help, you've switched the compander but if one of those had an intermittent problem (odd as that would be), it could potentially cause a problem downstream...

Definitely a tricky problem that either I'm missing an obvious answer to or is just uniquely strange.
Title: Re: Dandy Horse - no output
Post by: Vivek_rc on September 10, 2020, 05:38:50 PM
Hi Scruffie

I removed IC1 and IC6, and upon startup voltage on pin7 of IC2 was sitting at 7V, and after a couple of minutes itís now sitting at 14.15V, and remaining at this voltage.
Title: Re: Dandy Horse - no output
Post by: Vivek_rc on September 12, 2020, 04:29:06 AM
Hi Scruffie

Iíve been trying to troubleshoot further, checking for an shorts or bridges and at the latest check of the voltages on IC2, I see The voltage on pin 5 and pin6 of IC2 is now at 1.2 V and pin 7 still on 14 volts. All the other pins on IC2 are as per the expected voltages. Iíve reflowed all the solder joints as well. Audio probing the signal path it does work up until the output of pin 11 and 10 of IC2.

Really scratch my head with this one
Title: Re: Dandy Horse - no output
Post by: Govmnt_Lacky on September 12, 2020, 02:09:55 PM
Do you have any electro caps that are rated at less than 25V in the circuit?

Just trying new ideas  ;) ;)
Title: Dandy Horse - no output
Post by: Vivek_rc on September 12, 2020, 05:23:47 PM
Hi Mate,

non of them are below 25V. But what I am planing to do is replace all the 22uf caps with Panasonic caps and also replace the 220uf cap as well. Should get them by Monday. This replaces all the electro caps from Tayda.

Keeping throwing forward any ideas, all appreciated and will be tested
Title: Re: Dandy Horse - no output
Post by: Haberdasher on September 12, 2020, 05:42:28 PM
Sometimes when I have a weird voltage/amperage problem I can't figure out I've solved it by re-booting my power supply, changing out the power cable, or even changing which port the cable is plugged into.  Then again, the power supply on my bench is one of those cheap $30 ones from Amazon, so...
Title: Re: Dandy Horse - no output
Post by: Vivek_rc on September 12, 2020, 07:40:45 PM
That's the type i am also using  :). I just powered up the pedal just then and it's working perfectly. Disconnected power  and reconnected, working as expected, voltages on IC2 all check out as expected values . But if i keep it running for some time then the problems start. I will next power it with the isolated power supply from my pedal board, see if it makes a difference. but will also replace all the remaining electro caps from tayda with panasonic ones and hope by some luck it fixes it :).
Title: Re: Dandy Horse - no output
Post by: Vivek_rc on September 13, 2020, 05:20:39 AM
Iíve had some success running the pedal with an isolated power supply, getting a modulated output and itís been running on a loop for a few hours now. However there is a fair bit of white noise coming through as well.

I will replace the 220uf electro capacitor (I think for power filtering, I used an old one I pull out of another test circuit), with a new one thatís coming in this week, hopefully gets rid of the white noise. I have already replaced the two 100uf caps on either side of the 78L15.
Title: Re: Dandy Horse - Resolved
Post by: Vivek_rc on September 13, 2020, 11:47:23 PM
Hi All,

Just an update, replaced the 220 uf Electro CAP, still getting some white noise in the output, but maybe be due to background interference. Will box it up and see if it goes away.

i think the main culprit was my 9v power plug power supply. Running on an isolated 9V supply, the voltages on IC2 is staying constant and circuit is working well. Also replaced a few Electro caps along the way in my troubleshooting so not sure if they also contributed to the fix.

One thing i can say is the quality of the PCB is really good, multiple desoldering and soldering of the same components in some cases, pulling out components, the PCB solder pads and tracks have held up really well.

Thanks again for all the support