Help with suspicious power supply on a Digitech RP1000

[Strikerj]

Hi everyone, first post for me and just wanted to say awesome site so far, like what I see

Anyway ive got this RP1000 guitar processor here which I got from that great place called Ebay
Now it seems the unit turns on and has a display but no signal on the outputs including headphones.

Pulled it apart and found someone with sub solder skills (could have been worse) has had a go at it and made a dogs breakfast out of it.
I got my hands on the PSU schematic provided by Lostfollicles Thank you very much and repaired and rebuilt all effected parts.
to the best of my ability. (some parts on order)

I have a habit of testing the circuit before powering it on and found something that I think is wrong.
The +1.8v Vout track from U30 (chip removed) reads 3.5ohms to ground. now I think thats wrong. seems to be the power supply for the DNA2 chip.

Is this safe to turn on or will the MB be fried again? (earth pin on U30 was burnt away before i got it)

If anyone can answer or help with this It will be you (Awesome) guys
Schematic suppled below.
RP1000 Power Supply.pdf

Thanks again

[soundguruman]

Generally Digitech is intended to run on 100 volts AC.
It is relabeled 120 volts...and sold in USA.
This result is the power supply running very hot, and has a shorter life expectancy.
These problems show up all the time with Digitech...

Somebody sold you a defect. You should have sent it back for a refund.

It should be repaired by a professional, with test equipment. Otherwise you are just guessing.

Is it too late to return the item?

[Strikerj]

Hi soundguruman thanks for the reply

to answer the question I got it knowingly not working but unknowing that someone had tried to repair before.

I do have skills and test equipment and this is not my first equipment repair.
Im no pro but am proficient enough not to make it worse.

Ive already located the original fault the first guy missed but the cause is unknown.

Ive got no mediate intention to return it but want to test my skills in repairing it. so far I think im 90% there

[Strikerj]

Oh it just clicked sorry Im talking about the internal power supply's inside the RP1000's mainboad and not the adapter.
My adapter is fine
sorry about that, I must not have been clear on that. My bad.

[Enzo]

Not your fault strikerj. Welcome to the forum.

This 100v thing is a fiction Soundguruman has made up and still spreads when he can. It is his equivalent of a conspiracy theory.


As you clearly already understand, the only difference between operation on 100v and 120v would be the power adaptor. And those are correctly specified.

[Strikerj]

Thank you for the welcome,
Question, do I have a problem with my processing chip on the MB as the impedance measured across C232 is less then 4ohms.
I have isolated the power side of the circuit to eliminate possible shorts in that side of the circuit. all caps seem fine when tested.
should I remove the 144pin DNA processor IC and test again or is it highly unlikely?

[Jazz P Bass]

Have you removed C231 & C232?

If the 1.8V rail only feeds the 144 pin DNA IC & is bypassed only by C231 & 232.......

Caps removed that leaves the IC.

[Enzo]

And the copper/solder that connects it.

[km6xz]

What is the reading when shorting the meter test leads together? If you do have some resistance, subtract that shorted lead value from your 4 ohms. If is 2-3 ohm it would suggest the IC or it nearby bypass caps. Bypass caps failing is more common than LSIs, and a lot cheaper and easier to get. Check between digital ground near the chip and the 1.8v line on the IC. If it is lower than the reading at the power supply end of the trace, it is probably a bypass next to the chip.
Good detective work getting this far....

[Strikerj]

What is the reading when shorting the meter test leads together? If you do have some resistance, subtract that shorted lead value from your 4 ohms. If is 2-3 ohm it would suggest the IC or it nearby bypass caps. Bypass caps failing is more common than LSIs, and a lot cheaper and easier to get. Check between digital ground near the chip and the 1.8v line on the IC. If it is lower than the reading at the power supply end of the trace, it is probably a bypass next to the chip.
Good detective work getting this far....

Thank you for your time km6xz, my meter leads are 0.07 shorted ohms and the reading is 3.57ohms across the C232 solder pads with caps removed if I dont zero out my meter.
Thanks for the advice ill check it out and get back to you.
I might remove the IC if I cant find any leads on the short or get anywhere and I guess that should show me for sure.
Hope its gonna work out.
Ill keep you posted

[g1]

Can you just lift that IC pin, rather than removing the IC?

[Strikerj]

Can you just lift that IC pin, rather than removing the IC?

Good idea but im afraid to break a pin. Dont want to work harden the pin but ill remove the solder and lift the pin/pins up ever so slightly.
Thank you g-one

[Strikerj]

Have you removed C231 & C232?

If the 1.8V rail only feeds the 144 pin DNA IC & is bypassed only by C231 & 232.......

Caps removed that leaves the IC.

Hi Jazz P Bass, Yes i have isolated the circuit but don't have the rest of the schematic to trace if the track goes elsewhere. Ill look over the MB again and see if i can trace the track after removing the IC.

[Strikerj]

Removed all caps but no change. The IC was removed and short gone.
Should I be happy or sad?
Where do I find a chip? any suggestions?
I think this it one
72-1002 Qfp Ic - Buy 72-1002,72-1002 Qfp Ic Product on Alibaba.com

[g1]

Not sure what that chip does or if it is a custom version of something programmable? Would suggest trying to get it from Digitech first, then maybe if the price is outrageous check for alternatives.