ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
greetings all,
well, I thought I could rest for a while from Beomaster 8000 restoration, but.....
do you say NO to a friend in dire straights.....?
so, here it goes:
this BM came to me with the task of recapping the BM - it hasn’t been done in over 35 years and
it wasn’t starting the owner complained.
so, I recapped all boards, replaced the two trimmer on the output amp boards, replaced both relays
although I was not convinced the original relays were at fault 🙄
i deoxited all pins /plugs from all connectors, re-assembled all the boards and......no go, no double click, no sound ??
when I connected to mains the display came on without even touching the keyboard but no clicking
from the new relays.
unplugged again and heard the double click, plugged-in again and same outcome except this time i could here more than than double click, meaning the relays disengaged straight away....thinking immediately of fault switch engaging.
to make matters worth, the keyboard was inoperable except the vol & tuning wheel.
The BM would only listen to the remote control, but still not switching on.
after some extra checks on the recap work i disconnected the output amp boards one after another and now finally i could switch on the BM, but only via the remote ???
a problem surfaced, coming from the left output board - leaving the right output board connected I can still
turn on and off, getting sound but......I can not adjust the no-load current despite a working right channel plus
the keyboard is still inoperable ?
i am totally gobsmacked...after all the work.
been through various posts already, but all this makes not much sense......can you shed some light here,
pointers, suggestions ??
please.....thank you guys
ALF
Some first better news:
the keyboard is back on board after taking IC3 (master uP) out of its socket and deoxited the socket contacts.🙏
still unable to adjust the no-load current on the right (working) channel ??
the issue with the left output amp board remains - just the one that is particularly tricky to get to...lovely.
now the question is:
are the designated darlingtons of that channel likely to be at fault or is the culprit more likely on board #5
i’d go for board #5 as I worked on that one....will keep you posted.
Further good news:
after revisiting the left output amp board I detected a not bonding solder joint on one of the bigger freshly installed capacitors...very hard to see !!
i am using a new solder tin with a higher copper content apparently for better and stronger bonding....I wonder ?
the unreliable contact issue of the master uP and its old sockets is really crying out for replacing both the uP sockets to tulip style goldplated ones !!
the receiver produces sound but I need to revisit the no-load current adjustment and DC offset issue !!
the other thing that may be also related to oxidised contact is the memory function ?!
i noticed the designated memory chip also sits on one of these cheap old style sockets ?!
looks like more work, but for now we are breathing again - isn’t that nice 🤗
entries for your comments haven’t closed yet 🙄
Well, news can always get better.......
i ‘ve gone the extra mile and replaced the old sockets for the two uP IC3/4 and the memory chip as it can only improve things/contacs.
i remembered one blog on Beolover, when Rudy discovered the uP board is actually a double-layer board....🙄😡....and being bent and subjected
to changing temperatures may show after some 35 years in service...pointing to a healthy level of mistrust in terms of track fractures etc.
especially when BM have been subjected to previous repairs (as this one clearly showed)
new tulip-style sockets have certainly improved things - the chase is now on for certain spare parts like the opto assembly at the vol wheel - it has been
totally damaged to a point that it won’t fit anymore !
thank god for the remote control 🤗🙏
one much more pressing issue is: i can not adjust the no-load current ?? Managed to adjust the DC offset though. The no-load current trimmers are
new 100 ohm Piher trimmers....what is going on here ??
the BM plays, but without the correct no-load current adjustment........I feel very easy about that.
Any ideas or leads ????