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VR2023 with bad tape path stability

Geplaatst: 10 jun 2024, 20:49
door Whaka
hello,

a friend of mine asked me to try to bring to life a VR2023 (well, actually it's a B&O 8804V).
the first issue was a crazy clicking reel brake solenoid an no operation of any motors, was an esay one > missing +12Vb due to broken solder joints on a rectifier.

but now it live again, the mechanism have an issue i never saw before : the tape get badly drived on the drum entry side.
it slide up on the fixed guides leading to a very very poor tracking/noise bar.
the tape back tension work as expected, and really no abnormal tension on take up reel, and the guides glue is still intact.
pinch roller is totally excluded, it's in very good shape, and the exit path is good, and absolutely no phasing fluctuation in sound.

it has a last issue, but i don't think it's directly related, the head drum have a "hard point" meaning it doesn't spin really freely and lead to horizontal sync wobbling. i tried to get the head drum off to see what happen under, but nope... totally seized on the shaft.
i think i'm just gonna replace the whole drum unit, and i should get one soon.
but for the moment, i don't think it really cause an issue to tape path anyway.

so if someone have an idea on the tape path issue?
thanks :)

Re: VR2023 with bad tape path stability

Geplaatst: 11 jun 2024, 10:19
door gromsound
hi again, always nice getting these puzzles from you :D

how about the left threading 'cart' ? they are rather wobbly, maybe one is too loose on the rail or on the carrier. it should slot firmly in the end stop when threaded in. this position is critical.
as shown on my website, if the threading cord is dislodged from the pulleys the end stop will not be reached leading to wrong tape guiding. check all white pulleys including the small ones behind the deck. lubricate the threading rails a bit with wd40 or silicon grease.

Afbeelding

by the way: NEVER 'adjust' the tape path by screwing on the guides/end stops, these are factory adjusted using special optical tools. impossile to restore once disturbed. hope nobody touched that, check the paint spots.

you can however exchange the complete 'micro world' = the whole assembly with head, motor, upper and lower drum and tape path.
try knocking the shaft from above when pulling the upper drum.

Re: VR2023 with bad tape path stability

Geplaatst: 15 jun 2024, 08:16
door Whaka
hello :)

i'll check pulley at the back, i didn't think about them.
the cord was out of a pulley, but on the right side (so not the faulty side). it was in threaded position when i got it, easy to put the cord back in place. don't know why it jumped out, but i guess it was when solder joints went bad on the rectifier and certainly lead to weird behaviour on a lot of things.

it looks like nobody touched the guides, glue is still intact. but it's not always a guarantee anyway...
but it seems to correctly lock the threading guide, there's no play when engaged.

maybe this one get dropped at some point, i don't know...

Re: VR2023 with bad tape path stability

Geplaatst: 15 jun 2024, 12:10
door gromsound
as stated on my website, the cord can come loose if the machine is threaded in -without preliminary cleaning and lubrication- after very long time, the carts will have high resistance in the dry rails and on the way back they will 'hang' and the cord tension is momentarily lost => jumps off the pulleys. before you see that...
the machine will not stay in play that way, it detects the cariages are not seated in the end stops correctly.

so there is an additional fault. check the infrared leds of the threading detectors, they are connected in series so one defect is all out (see the schematic diagram in the manual).

Re: VR2023 with bad tape path stability

Geplaatst: 16 jun 2024, 09:50
door Whaka
there's no issues with optocouplers for sure, as it work "correctly" if we except the bad tape path and the hard point in the head drum.
as i said, it was in threaded position when i got it, and the cord was already out of the pulley, i forgot to say that :D
but because of bad solder joints in power supply, the first time i've plugged it (and after put back the cord in its pulley) the only thing it did was a crazy clicking brake solenoid.
then i found bad joints in PSU, and after reflow, everything came back to life and it went back with no troubles in stop position.

so yes, maybe the cord jumped when it was waked up the last time someone else tried it, or maybe when solder joints went bad in power supply. it's hard to know what happened exactly in its past life anyway.

Re: VR2023 with bad tape path stability

Geplaatst: 16 jun 2024, 11:00
door gromsound
ok thanks for clarifying :)

strange it remains. slack tape would normally not lead to bad threading, only a noise bar in the middle of the screen. if all guides are still 'painted' one would nog suspect bodging in the past. maybe it fell down? is the whole 'microworld' still correctly fitted in the chassis?

last thing i can think of, is the cassette positioned correctly on the supporting points of the deck? normally this is only an issue with the later generation due to a split plastic cassette guide pin. the older ones are built more solid.

Re: VR2023 with bad tape path stability

Geplaatst: 20 jun 2024, 07:43
door Whaka
gromsound schreef: 16 jun 2024, 11:00 maybe it fell down? is the whole 'microworld' still correctly fitted in the chassis?

last thing i can think of, is the cassette positioned correctly on the supporting points of the deck? normally this is only an issue with the later generation due to a split plastic cassette guide pin. the older ones are built more solid.
that's a possibility, maybe it was dropped in its life. there's a lot of broken plastic on the cabinet, so very likely it could.
the microworld appear in good conditions, the 3 big screws that hold it are intact and came with no issues.
the tape carriage is fine, and the cassette "sit" correctly. i still didn't looked at the rear pulleys, i'll do that soon :)