Bel BD-80 memory upgrade and repair

Hi everybody

wondering if there are any Bel BD-80 users around here ?

I have two units here, one working and one on the repair bench

Got an extra memory card and would like to expand the delay / sampling time in the working unit

I have tried just popping the card in each of the four slots but the delay time is not increasing

I have noticed that the broken unit has got only one socket for the memory cards. The remaining three are left empty, without connectors soldered on the pcb.

The working unit has connectors on all the four slots, and I also notice there is a header with some jumpers. On the single slot unit this header is replaced by 0 Ohm resistors

My guess is that in order to enable the memory cards these jumpers need to be set in some particular order. I believe that the unit with only one slot was a non-upgradeable version thus there was no need to have the jumpers

If there is anybody who knows this delay and has experience in upgrading the memory, please let me know.

An user manual would probably have solved the mistery, but I couldn't find it over the internet

i bought a manual from an internet page but the memory upgrade wasn't mentioned ...

just tried removing some of the jumpers and got the right combination to enable the extra memory card

now i have to go ahead fixing the broken one. it is quite hard without a schematic but at least I got a working unit to compare to

some ics are getting hot so i have ordered replacements, they are just standard logic ics so just cheaper to swap them all out. if the a/d or d/a are busted, that's gonna be a bigger problem, because these are harder to find

i have attached the manual in case some will need it in the future

these are some service notes that might be help with debugging

unfortunately no schematics

https://groupdiy.com/index.php?topic=65816

This is what I have..

yep, that's pretty much what is available online

bel is still in business, but didn't reply to my requests for schematic, even though this has been discontinued for ages, and the company makes different products today