ADA Depot Too - A Forum To Support Users of ADA Amplification Gear

Let's Get Technical => Troubleshooting Problems => Topic started by: Wormwoody on March 22, 2018, 05:04:51 PM

Title: MP1 v 1.38 no sound can someone help me out?
Post by: Wormwoody on March 22, 2018, 05:04:51 PM
I have an older 1.38 MP1 and it whaled but a bit noisy. So I got a good soldering iron and went to town installing the noise kit, some diodes, caps, battery mod, and a few other things from MJMP. Now I don’t have sound from tube clean or tube dist but SS works. I don’t know what I did and am wondering if someone can walk me through a troubleshooting process???

Thanks!
Title: Re: MP1 v 1.38 no sound can someone help me out?
Post by: Iperfungus on March 22, 2018, 05:18:07 PM
The one and only: MJMP!  :thumb-up:
Title: Re: MP1 v 1.38 no sound can someone help me out?
Post by: rnolan on March 23, 2018, 02:37:25 AM
Hey Wormwoody, MJMP will no doubt help you get it sorted.  Good news that the SS works.  My guess is the signal isn't either getting into the tube circuit or out of it, or there's an issue in the tube circuit.
Did you do any work on the tube board ?
Are all the tube board connections to the PCB how they should be ?
Are the tubes ok ? and are they lighting up ?
Did you change the transformer ?

IIRC the SS input/circuit basically bypasses the tube section, also remember the OD2 setting controls the amount of compression in SS mode.
Title: Re: MP1 v 1.38 no sound can someone help me out?
Post by: Iperfungus on March 23, 2018, 02:53:12 AM
I agree: looks like something failed into the tubes board.
Title: Re: MP1 v 1.38 no sound can someone help me out?
Post by: MarshallJMP on March 23, 2018, 10:10:37 AM
Rnolan already made some good points, start there. Do the tubes light up? Do you have high voltage on R1 and R4 on the tubeboard?
Title: Re: MP1 v 1.38 no sound can someone help me out?
Post by: Wormwoody on March 26, 2018, 06:51:12 PM
Haven’t checked this in a few days I expected an email notification if there was a reply. Anyways I will crack the case again and check out these things tonight.

Rnolan—I did do some work on the tube board. Changed some caps mainly if I remember right.  Also now that I think about it I also removed the main signal wire out or in (not sure which) in order to more easily swap caps on the tube board (with it connected it was tight). I extended that wire with a piece of scrap in order to more easily remove tube board in the future. Thankfully MJMP caught this when I sent him a pic and told me to put it back to normal. I did ring it out with my ohmmeter and seems as if connection there is good. Thanks all of you I’ll reply back when I have checked voltage and looked if the tubes are glowing (if I remember right they are). I believe all the tube board connections are as they should be, is there any I should check in particular?  I did not change out the old xfmr.

Thanks MJMP I’ll check voltage at those points.

I am an electrical contractor so I can do some of these things easily but I am new to PCBs and soldering in general.

Thanks again gents.
Title: Re: MP1 v 1.38 no sound can someone help me out?
Post by: rnolan on March 27, 2018, 12:37:49 AM
Unfortunately email comes and goes (but just for some of us), I'm not getting any notifications at the moment either, best to check the site from time to time  :thumb-up:
Title: Re: MP1 v 1.38 no sound can someone help me out?
Post by: Wormwoody on March 29, 2018, 12:16:47 PM
The tubes are lit up. I have 189V to ground on the incoming power side of both R1 and R4 and 174 V to ground on outgoing side of both R1 and R4. So power is getting onto the tube board through R1 and R4, and to the tubes (if they’re lighting up) but somewhere else on the tube board (or afterwards) it is not getting to the outputs. Where could/ should I look next for power/ signal?
Title: Re: MP1 v 1.38 no sound can someone help me out?
Post by: Wormwoody on April 01, 2018, 09:47:33 AM
Does anyone have any additional suggestions to troubleshoot this mp1?  A while back MJMP suggested my five pin LED things (can’t remember their name) that I replaced may be bad. I bought them from a website called Pedal parts, or a similar named company. Anyways as per his suggestion I tested them (as per pedal parts test procedure using 9v and a resistor) and they tested good. Are there any resources showing a signal chain out of the tube board that I can use to troubleshoot, or does anyone have any further ideas?  I’d like to find the problem myself (with help from you guys), but if I can’t figure it out can I send it to one of you to be looked at?


Thanks again!
Title: Re: MP1 v 1.38 no sound can someone help me out?
Post by: MarshallJMP on April 01, 2018, 01:20:58 PM
Those led things are called vactrol's. So those voltages look good to me.
Do you have access to a oscilloscope?
Title: Re: MP1 v 1.38 no sound can someone help me out?
Post by: Wormwoody on April 01, 2018, 05:30:13 PM
I do not have access to an oscilloscope but I can ask around.
Title: Re: MP1 v 1.38 no sound can someone help me out?
Post by: MarshallJMP on April 02, 2018, 10:15:55 AM
That would be a lot easier to find what's wrong.
Title: Re: MP1 v 1.38 no sound can someone help me out?
Post by: Wormwoody on April 02, 2018, 03:27:06 PM
Looks like there are some reasonable ones out there on flea bay. What specifications would be needed for this application?  Would I also need a signal generator and a load bank?
Title: Re: MP1 v 1.38 no sound can someone help me out?
Post by: MarshallJMP on April 03, 2018, 01:51:15 PM
Well a signal gen is also great to have, nothing fancy is needed, if it goes to 20kHZ it's fine.
As for the scope a dual trace 20MHz is more then enough. If you need assistance you can always mail me with what you found and I can have a look.
Title: Re: MP1 v 1.38 no sound can someone help me out?
Post by: Wormwoody on April 09, 2018, 01:56:48 PM
Thanks MJMP!  I sent you an email about oscilloscopes and possibly getting a price on shipping the preamp to you to get serviced.
Title: Re: MP1 v 1.38 no sound can someone help me out?
Post by: MarshallJMP on April 10, 2018, 12:53:08 AM
Mailed you back with some suggestions.
Title: Re: MP1 v 1.38 no sound can someone help me out?
Post by: Wormwoody on May 05, 2018, 10:06:19 AM
I got an analog oscilloscope, a signal generator, and some 10x probes ready to go—if you’re able to coach me through it MJMP.