Revox A77 Tweak

[Marcel K-O]

Hi, this is my first post and my first tape machine Revox A77 MIV HS. Im hoping someone might be able to help me.

The seller stated to me that it was near mint ,set up,and ready to go and he had it set up for play back when I went to see it. It looked and sounded great. I bought it, took it home tried it out and started to find not so near mint anomalies.

1) fast forward break not so good when I hit stop
2) right and left channels output off center, must adjust pan control for center image
3) front face plate laminate slightly separating above transport controls and VU meters ( no big deal )
4) not sure about this one but the first tension tape guide has a groove on it I can feel with my finger tips. Is that ok?

Any way my main concern is #2
I ran a test tone into the aux inputs and the VU,s showed a perfect balance of input ch1 and ch2 but monitoring with speakers and headphones output showed that ch2 is louder than ch1 .( No tape was loaded on the deck in this observation )

I was wondering if I could regulate the balance buy adjusting the trimpot of circuit P 108 . I just want to run a signal straight in and out to balance the output signal. See attachments.

Or maybe Im way off and it has something to do with caps? I don't know..

Any way I hope this is something I can remedy myself, but if not I could try to find a tech in town....I hope

best regards
Marcel

 

[jpmorris]

I can't really help with the amplifier circuit, but regarding no.1, the A77 is one of those machines where going straight from fast-forward to stop is a bad idea.
I have a feeling the later designs may have added an interlock so you might be safe, but in the earlier models in particular, it could stretch the tape. What you were supposed to do to stop a fast forward was hit rewind, which would then gradually slow the tape down and then hit stop when it was slow enough.

 

[Marcel K-O]

Thanx for your reply, Yes I rock the reels to go from ff to rewind to stop..

After reading over the service manual last night I opened the deck up and found that it has never been calibrated, because the paper sticker that covers the trim pots for alignment have never been poked. (Factory Calibration)

Any way I'll be taking this machine in to a service shop one day , but not until I get some use out of it first, I just got it..Now I'm waiting for some tape to come in

Thanx again

 

[deejayb]

Hi,

I'd be really interested to hear if and how your problem 2 was solved - "right and left channels output off center, must adjust pan control for center image"?

I recently bought a Revox A77 which seems to have the same or a similar problem. Mine monitors a test tone accurately, but if I then record it to tape, the playback on ch2 is significantly louder than ch1.

Many thanks.

 

[leddy]

Any way my main concern is #2
I ran a test tone into the aux inputs and the VU,s showed a perfect balance of input ch1 and ch2 but monitoring with speakers and headphones output showed that ch2 is louder than ch1 .( No tape was loaded on the deck in this observation )

I was wondering if I could regulate the balance buy adjusting the trimpot of circuit P 108 . I just want to run a signal straight in and out to balance the output signal. See attachments.

Do you have an MRL test tape?

 

[leddy]

Aw crap...necro post.

Carry on.