REVOX A77 VU Meters

[Ozzdownunder]

Hi, I have just replaced a set of VU meters with the same but improved Australian Made. Problem is when switching on the unit the VU meters swing completely to the right side. I checked the colors of the wiring and these are the same as the original fitted ones. Also should the VU meters bulbs behind the meters light up on playback? I checked the bulbs and these show a complete circuit on the multi-meter. Is there any other way to test the old meters as one used to just get stuck. I am aware these do not work on playback only on record. Should it light up when pressing all the red record buttons or should I be pressing the play button as well.

[SteveCG]

I believe the VU meters are operational on playback for the Dolby versions of the A77 only.

[Michael Maurice]

When switching on, the VU meters do indeed swing to the right, this occurs on all models. The only lamps which should be lit are the Power lamp, the lamp between the VU meters and the EOT lamp.

The lamps behind the VU meters are only lit when the appropriate REC button is depressed and the machine is started in Record.

[Ozzdownunder]

OK this is a non Dolby version. When switching on power the VU meters stay in the right position. The meter indicator arms do not return to their normal resting position. I suspect it could be the capacitors on that PCB that may need to be replaced. Also is there a diagram available on this model where it shows the PCB'?, Thanks for your prompt reply, it's appreciated.

Meantime all the best for the New Year 2021 from Down Under Australia.

[Welsh Anorak]

Just to clarify, you need to depress one or both record buttons by the meters, then record and play on the main switchbank to get the lights to come on. The meters should work anyway when an input is present or when the monitor rotary switch is set to play (NAB or IEC on standard models). The meter switching is slightly different on the Dolby Mk4 versions.
I didn't know A77s were made in Australia. How do they differ and which versions were they?

[Michael Maurice]

I think the OP is referring to the VU meters that are supplied by Nagravox in Australia as a direct replacement for the originals.

The service manual is available from HiFi engine.

The VU meters should not stay in the RHS position. There are no capacitors on the switch board, the feed to the VU meters comes from the Record board. Check C509, better still change ALL the small electrolytics especially the little white ones.

[ms660]

Just for info, in the schematic the B+ supply to the bulbs is via the record channel switches (Board B) and the connection for both bulbs to 0v is via the series connection of contacts 7 and 11 on relays A and B (Board F) pressing Play energizes relay A while at the same time pressing Rec energizes relay B.

Lawrence.

[Welsh Anorak]

Ah - should have read the post more closely!
Since the originals worked after a fashion, it's likely something was disturbed in their replacement. I'd check the location of the boards and wiring.
Are they always stuck to the right or do they vary with the input controls and switching being adjusted? I can't easily see what both meters have in common to cause this.

[Welsh Anorak]

The OP sent this message to my email address - I think it might help so I'm posting it on here with his permission.

Hi,
I did try to find out if turning any of the input/output controls would make any difference and no nothing changed.
When I checked the old VU meters they both showed on a multimeter that there was no open circuit. But one of the indicators was completely stuck
to the right position and only when I removed that one a knocked the meter that it would be unstuck. But I thought that this is a problem with some of the original Revox
indicators with the glue used inside the meters. The new Australian Nagravox, not cheap $192 aud a pair but are better. But the old indicators did not stay
to the right when switching on the power. Mind you I did spray some contact cleaner on the PCB to clean the wiring connections, just in case and it seemed
to be coincidental that it happened after all this. But I cannot see what difference that would have made.

[Michael Maurice]

I'm minded to ask what would happen if he fitted the original meters back in the machine.

Otherwise it doesn't make sense.

[Welsh Anorak]

I suggested this to him but haven't heard anything. Like you, I can't see any electronic fault that would cause both meters to show FSD unless it's something done in their replacement - he does mention contact cleaner so he may have removed the modules and disturbed something.

[John_BS]

C509 ausgeput /very leaky.

John