Digitech RP1000 Guitar Processor

[Lostfollicles]

I recently bought a Digitech RP1000 guitar processor on ebay for what I thought was a bargain price! Yepp! I know, I should know better but to be fair, I had no problems with it until I was gigging with it outside in the sun and the power supply was noisy! By noisy! (I do live in Spain) I mean I suspect the three phase power supply into the building was unbalanced, the gig was a restaurant and they had electric chip friers and every time they turned them on, It was causing uneven harmonics which produced a rather unpleasent loud hum which could be heard on the P.A. system! Getting back to my problem! The RP1000 cut out intermittantly and re-booted which was very annoying and I put it down to just the crappy power supply at the gig, however I had the same problems while rehearsing with no power supply issues, so I sent Digitech an email to ask if there were any problems with this unit which of course they denied!
As the unit is out of warranty I decided to investigate, I pulled the unit apart took shorting precautions and turned the unit on via it's 9Volt AC adaptor which I also checked for output voltage, which was reading a healthy 8.9Volts on load.
As I suspected problems with the AC to DC power supply section I checked to see if the four S1g diodes in bridge-form were causing any problems! I checked their temperature and they were cooking at well over 60 deg C. As I needed the unit that night for a gig I decided to make a U shaped heatsink from a small piece of aluminium which sat on top of the diodes and the chassis and applied heatsink compound on the tops of the diodes and the chassis put it back together and crossed my fingers! It worked!! I have had no problems since but of course I am not happy with this solution so decided to change the 1 Amp S1g's diodes for 3 Amp S3G's diodes and have ordered them to fit very soon even though I know they are slightly larger! I also supspected faulty capacitors aswell but have no way to test them.
I did send Digitech an email to tell them of my findings and they just said change the diodes!? To what? S1g's or S3g's?????
Another email later they were kind enough to send me a pdf schematic of the power which considering the RP1000 is still in production, I think is a real achievement!
RP1000 Power Supply.pdf

Sorry to bore the pants of you guy's but any help would be great!

[mozwell]

if the diode case is only 60C, thats not really hot, if they were over 100C i would start to be worried.
It will not hurt to change them to the bigger diodes.
You should check all the various voltage levels in the power supply, as they are marked on the drawing. +/-15V, +5V, +3.3V, +1.8V
Check all the ic's & other diodes to see if any are hot.
If you are replacing electro's make sure they are suitable low esr types, if you can use 105C caps instead of 85C ones.
C22, C47, C90, C107
I woudl also look at those 10u 16V X7R caps..... you could put a 10u 16V tantalum cap in parallel with the existing ones.
Check the AC ripple on main electro filter caps, if they are not filtering properly, the ripple may "reset" your unit.....

[Steve Conner]

That's not an overheated diode,

THAT's an overheated diode!

I think it's more likely that the heatsink is cooling down some other component like a voltage regulator. Diodes don't shut down when they overheat and then work again when they cool down. They either work or fail catastrophically.

[Enzo]

so I sent Digitech an email to ask if there were any problems with this unit which of course they denied!

The question is assumed to ask "are there any consistent problems with this model unit, and if so are there any engineering changes that correct it." If they have not had an overly large percentage of these units coming back with failures, then they can honestly answer the question "no". All circuit failures are not due to consistent systematic failure modes.

I'm with Steve here, I'd be wagering your removing heat from the diodes also reduced the heat around one of the low voltage regulators. If one of those regulators were to drop out, it would cause the system to reboot. If the area of the circuit board runs cooler, then a marginal Vreg may keep running.

You were talking to customer service representatives at the company, not the engineering staff. If a customer reports he is having trouble with the diodes, they will just recommend new diodes. If we can imagine that the vast majority of these units do not have this problem, they won't see the need for engineering changes

[g-one]

The problem was likely due to the poor power in the building rather than the RP1000. Not the noise but the voltage sagging when the chip fryers kicked in. The mains voltage drop would cause a drop at your 9VAC adapter. This would result in a drop at the 5V regulator which would cause reboot as Enzo has mentioned.
The diode temp. is probably normal.
Digital equipment needs good mains power. Unfortunately, places that host gigs (like clubs and restaurants) often have poor mains power. Not sure if it is still the case but some musicians with digital based equipment used to have to use UPS modules to make sure their systems did not crash.

[Lostfollicles]

Thank you guy's for all your input! As an electrician by trade not an electronics technician I suppose I was dumbing down my observations because of a lack of knowledge regards electronic circuits, So thank you again this is a serious learning curve for me! I think Enzo has hit the nail on the head, it does indeed look like a voltage regulator problem but I also agree with mozwell, I think it would certainly be worth my while changing out C22 & C47 first as I suspect that these caps have dried out! I have not made any changes as yet to the RP1000 as my "Bodged heat sink" remedy has sort of worked but I did notice at a gig recently that I was getting a gradual increase in hum now and again when the RP1000 had been on for sometime, which in my basic electronics understanding points very much at these two caps!
Thank you again guy's for your help so far, please don't hesitate to correct me if I am totally way off the mark!

[Lostfollicles]

if the diode case is only 60C, thats not really hot, if they were over 100C i would start to be worried.
It will not hurt to change them to the bigger diodes.
You should check all the various voltage levels in the power supply, as they are marked on the drawing. +/-15V, +5V, +3.3V, +1.8V
Check all the ic's & other diodes to see if any are hot.
If you are replacing electro's make sure they are suitable low esr types, if you can use 105C caps instead of 85C ones.
C22, C47, C90, C107
I woudl also look at those 10u 16V X7R caps..... you could put a 10u 16V tantalum cap in parallel with the existing ones.
Check the AC ripple on main electro filter caps, if they are not filtering properly, the ripple may "reset" your unit.....

I Mozwell thank you for your reply!
I was thinking to replace C47, C22 and C213 to 25 volt types first to see if that makes any difference, would it be OK for me to enlarge C47 to this: - Compre Aluminio 136 RVI Aluminium Radial Cap,25V,3300uF Vishay MAL213666332E3 en RS Online y lo recibirá en 24/48 horas. This is a 3300uf 25v low esr type, would this upset the circuit? Just thinking it might help to keep the voltage a little more stable if I get large voltage swings on the crappy mains supply over here in Spain!


Regards
Stefan

[mozwell]

Hi Stefan
Should be no issues changing C47 & C22 to 3300u 25V, low esr types, just make sure they fit in the available space.
i would also try soldering some 16V or 25V tantalum caps in parallel with all the 10u SMT X7R caps C118, C141, C228, C231, C89, C91, C108, C278, C279, C110, C92 watch the polarity !!! as the SMT caps used are not polarised, and these tantalum caps are polarised.
Maybe with the unit powered up, measure the voltage across each of these 10u caps & mark the positive end, then turn off the power & solder in the tantalum caps.
10u is a big value for an X7R smt cap.....

Did you measure all the supplies to see what voltage they were, you can also measure the input voltage to the voltage regulators, to see how much "power supply headroom" you have before the linear regulators start dropping out of regulation.

I would suspect that it is supply voltage "dips" that cause dips in the regulated supplies, and cause the electronics to "reset"
Changing C47 & C22 to 3300u will help with this.

[warunasanjaya55]

I live in Sri Lanka. Can anyone can give me a place except ebay to buy Digitech RP1000 Guitar Processor for my personal use ?.I also want to know present average prize of Digitech RP1000 Guitar Processor.

[J M Fahey]

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