STUDER A820 hardware and software upgrade path

[yjwu]

Hello:

Recently I restored a non-functioning STUDER A820. Now it works beautifully!

Its software configuration was as followed:

1) master MPU (820.786.21): 1.820.996.20                             : 38/86
2) capstan controller (820.764.26): 1.820.994.25                    : 35/88
3) tape deck MPU (820.785.21): 1.39.88 (?)                             :???         hard to decipered hand writing

According to STUDER list the most up to date hardware and software for A820 Mk-I was

Capstan:1.820.764.28       1.820.994.27                                  10/92
Tape Deck:1.820.785.26    1.820.995.24                                  35/95
Master MK: 1.820.786.24   1.820.996.22                                  06/89

Does STUDER's ftp site provide enought information for hardware/software upgrade to most up to date version?

How about the difference between Mk-I and Mk-II? I know the skimming and HX-Pro was inplemented on Mk-II. Is it possible to migrate from Mk-I to Mk-II?

yjwu

[Waltzingbear]

It is possible to use the MkII firmware in the MkI machines, you will not get the new features, but there are refinements that are useful. So, no, skimming and hx-pro will not work without hardware changes.

Alan Garren
Waltzing Bear Audio

[yjwu]

It is possible to use the MkII firmware in the MkI machines, you will not get the new features, but there are refinements that are useful. So, no, skimming and hx-pro will not work without hardware changes.

Alan Garren
Waltzing Bear Audio

Thank you for your information. Yesterday I followed the note on STUDER list and upgraded driver Darlington transistors on my capstan amp board to BD679, BD680.

First time there was tacho error: the capstan motor won't turn. Then I realized that the pin configuration for BU522, BW??? were different from that of BD679, BD680. (why the document was silence on this important difference?) I had to mount the transistors backward! Fortunately nothing was broken. Traces on the circuit board is quite fragile, it probably won't survive another run. Anyway, now the capstan motor board had migrated to .23. The wow and flutter in 4.75 ips was still not as good as expected. The shuttle-locked play does not engage capstan motor and pinch roller. Still not great.

Maybe there is small rub of brake band and lining?

I am still quite happy, previous experience from fixing A807, A810 was useful.

Maybe I will do the incremental upgrade on each hardware first.

Regards!

Y.-J. Wu