Boss - HR- 2 Harmonist

raymond · Post by **raymond** » 03 May 2013, 20:12

Does anyone happen to have the schematic for Boss Harmonist HR2 pedal? The pedal powers up and clean signal is going through and when effect is engaged (led goes on) the clean signal still heard but no harmonies. Without schematics I think I could check next the various surface mounted opamps and also feed a signal and check with a scope if the signal is processed. I have also ESR checked the filter electrolytic caps and no issues there and the 5V regulator is also fine (output 4.95 VDC). Something else worth to check?

Dirk_Hendrik · Post by **Dirk_Hendrik** » 04 May 2013, 05:48

Google for the PS3 schem. Same thing but different code in U10.

Edit; Here it is

boss PS-3.pdf: (1.26 MiB) Downloaded 398 times

raymond · Post by **raymond** » 04 May 2013, 06:22

Once again, thank you Dirk_Hendrik for your dedication. It seems that I may check HR2 using the PS3 service notes waveforms as guideline. I'll post when making progress in identifying the issue with my HR2

Dirk_Hendrik · Post by **Dirk_Hendrik** » 04 May 2013, 09:27

raymond wrote:It seems that I may check HR2 using the PS3 service notes waveforms as guideline.

Eehrm.. not completely. At least, I did not manage to perform all PS calibration instructions on a HR2 some weeks back. However, the first one, the Bias calibration with the 50% duty cycle, helped me to get that HR2 back from a noisy sputtery distorted beast to a normal fuctioning older-school harmonist.

That was after that schem helped me to trace the signal path replace 2 opamps (that were replaced once by "someone") and determine 2 via's were resistive, causing a part of the ground planes to be disconnnected from gound. I spend a day on that pedal, including trying to find out where that sputtery noise came from since it sounded like a leaking electrolit.

raymond · Post by **raymond** » 04 May 2013, 18:18

Duty cycle ok, no need to adjust the bias. It seems that the DAC (UPD6379) is kaputt or freezed ie. all inputs (clock, lrclock, data) are feeded with square waves, but no output from pins 5 or 8. Pin 4 (supply voltage) is ok. Also pin 6 (reference voltage) is ok or about 3.5 VDC.

Tried to locate supplier from ebay, but have to be specifically UPD6379 as other versions are for lower supply voltage (UPD6379L) or have different pinout (UPD6379A).

raymond · Post by **raymond** » 22 Jul 2013, 19:00

raymond wrote:Duty cycle ok, no need to adjust the bias. It seems that the DAC (UPD6379) is kaputt or freezed ie. all inputs (clock, lrclock, data) are feeded with square waves, but no output from pins 5 or 8. Pin 4 (supply voltage) is ok. Also pin 6 (reference voltage) is ok or about 3.5 VDC.

Tried to locate supplier from ebay, but have to be specifically UPD6379 as other versions are for lower supply voltage (UPD6379L) or have different pinout (UPD6379A).

Finally got a new UPD6379 and replaced the original, but no change to better (or worse). Any ideas where to look next?

Boss - HR- 2 Harmonist [schematic]