[Thinline]

Hi Marco!

I had the same problems with my ref 500 - i found out that the A/D converters (MC 144111) were defective, so the optocouplers didn't react and therefore: no sound! You can check this (pay attention to the very high voltage in the amp!!!) if you pull away one of the black castings of the optos - if there is no change  in brigthness when ypu turn the knobs then the A/D converters are bad!

greetings
Bernhard

[Thinline]

Hallo,
danke für die Antworten. Bei Dynacord habe ich nachgefragt. Leider haben sie die Hex-Datei nicht mehr. Haben mir freundlicherweise noch die Bedienungsanleitung als PDF geschickt. Einen antiken Brenner habe ich mittlerweile und konnte das Eprom (27C64) auch auslesen.
wie schon vermutet, sind nur noch Nullen drin. Wenn ich niemand finde, von dem ich das Eprom kopieren kann, werde ich wohl die Digitalplatine überbrücken.
D.h. die analogen Signal der Potis abgreifen und direkt auf den Vorverstärker geben.  Dummerweise sind die Signale invertiert. Da muß ich noch mit OP's die Signale nochmal invertieren. Dann kann ich ihn wenigstens als normalen Verstärker benutzen.

Hi! Hast du inzwischen den HEX Code gefunden - ich müsste den noch haben, da mir auch mal ein Eprom kaputt gegangen ist.
Grüße
Bernhard

[marcomeloni1979]

Hi Marco!

I had the same problems with my ref 500 - i found out that the A/D converters (MC 144111) were defective, so the optocouplers didn't react and therefore: no sound! You can check this (pay attention to the very high voltage in the amp!!!) if you pull away one of the black castings of the optos - if there is no change  in brigthness when ypu turn the knobs then the A/D converters are bad!

greetings
Bernhard

Hey Bernhard, thank you very much fir your reply! Im more of a Marshall/Fender point to point guy, dont have any experience with the digital side of amps. 
I see from the schematic that there are two different MC144111. Im assuming is one of these in the first photo and the optos are these? If yes, at least two have no light.  I csn see that one does...

[marcomeloni1979]

Hi Marco!

I had the same problems with my ref 500 - i found out that the A/D converters (MC 144111) were defective, so the optocouplers didn't react and therefore: no sound! You can check this (pay attention to the very high voltage in the amp!!!) if you pull away one of the black castings of the optos - if there is no change  in brigthness when ypu turn the knobs then the A/D converters are bad!

greetings
Bernhard

Are these In the first pic the possible faulty parts? Nd in the second pic, are those black cilinders the optos. I can see at least two dont light up...

[Thinline]

Hi!

If you can see only one opto lighting then botth D/A converters are faulty. If you look at the schematic you can see that opto I 004 is for the volume - if there is no ligt there is no sound! I would change booth mc144111 (i cant't see anything on your photo (too dark), but you can read the writing on the IC. Nearby the IC's should be written  "I 007" and I 008"  and on the IC "MC 144111". Please watch out for the right name of the IC's when you order them - should be MC 144111 P with 14 pins.
Another posibility for the malfunction could be IC  MC 14447 CP - this is the A/D converter and the heart of detecting your turning on the knobs.
The last possibility is that the optos themselve are defective. To be sure that that is not the case you can messure the voltage on the analog outputs of the  MC 144111 P while turning the knobs (very tricky, because there is rather smale place between the pins!!!) - if there is a change in voltage, then the corresponding opto (or the ribboncable from the digital Board to the tubeboard) is bad.
I hope this helps - dont't hesitate to contact me
Bernhard

[marcomeloni1979]

Thank you so much for you thorough answer Bernhard! I did order the correct A/D converters but it was very helpful to know about the change in voltage when turning the knobs. This amp makes servicing a point to point amp like changing the batteries in a remote control!

Is there an "up" and "down" when switching the MC144111P or both ways are fine? Also, to take out the board where the A/D converters are, is it just a matter to lever it out of its sockets? 

Thanks again!
Marco

[Thinline]

Hi!
It is not possible to lever them out of the sockets - they are soldered!
And what do you mean with: "Is there an "up" and "down" when switching the MC144111P or both ways are fine?"
You have to solder the new chips with the notch on them the way the outsoldered ones were in their places - don't make a mistake there!
You can pull out the whole digital board and place it on a antistatic surface. Make sure that you have no static electricity on your hands when you work on it!!
I found it not so difficult to work on these amps, because of the modular building of the boards (better than an eyeled board with wires running underneath!)
Good luck!
Bernhard

[marcomeloni1979]

Ok, thanks a lot for the clarifications. I only worked on PTP amps so far so this is gonna be a big step un in game.

Marco

[Thinline]

I would not solder the IC's directly to the board - instead of that i would buy two IC sockets , solder them and stick the D/A converters into them.
Bernhard

[marcomeloni1979]

I would not solder the IC's directly to the board - instead of that i would buy two IC sockets , solder them and stick the D/A converters into them.
Bernhard

Thank you for the tip Bernhard, although after a few google searches, i couldnt find any sockets for the IC's...

[marcomeloni1979]

Thank you for the tip Bernhard, although after a few google searches, i couldnt find any sockets for the IC's...

Scratch that, i did find them!

[marcomeloni1979]

I would not solder the IC's directly to the board - instead of that i would buy two IC sockets , solder them and stick the D/A converters into them.
Bernhard

[marcomeloni1979]

I would not solder the IC's directly to the board - instead of that i would buy two IC sockets , solder them and stick the D/A converters into them.
Bernhard

[marcomeloni1979]

I would not solder the IC's directly to the board - instead of that i would buy two IC sockets , solder them and stick the D/A converters into them.
Bernhard

Hey Bernhard, is it possible to convert the amp to analog only? Tried desoldering the D/As but the puns are so small i dont want to damage the board....

[Thinline]

Hi!
This makes no sense! There would be a lot of soldering an desoldering plus a new layout and you will end with a two Channel Amp. if you like the dynacord sound, i would rather buy a reference 602 - this is the analog version (two channels) of the 500/502.

Best regards
bernhard