ReVox B77 MkII - HELP - UK Vintage Radio Repair and Restoration Discussion Forum

cliofreak · 13th Dec 2016, 6:15 pm

Hey there,

I've acquired a beautiful Revox B77 and I'm determined to get it up and running nicely.

1. I have no power lead yet so don't even know if it will power on. I've one ordered.

2. When I do power it on, I can tell that I'll be doing nothing till I get a new capstan or possibly it's called a 'pressure roller' as the current one is all gummed up!

Anyone any ideas on how to get hold of one of these in the UK? Are they a generic fit or do they change size dependant on the machine?

Thanks!

Dunc100 · 13th Dec 2016, 10:37 pm

Hi Clio freak,

The B77 is a great machine, I'm still waiting for mine.

That pinch roller looks nasty and unfortunately I can't suggest anywhere in the UK for a replacement.

The rollers are different sizes for different machines so "any old" roller wont do. You'll end up with all sorts of mess going on, tape everywhere or chewed up. No one wants that.

There is a service provided by someone in the states who goes by Terry. I think if you Google Terrys rubber rollers he'll be on there. He refurbishes yours then sends you one back. No affiliation and all that but I hear he has a good reputation.

I presume you've checked those heads out or it'll be a dear doo.

Hope you get her running as well as she is capable as it'll be worth it.

cliofreak · 13th Dec 2016, 11:05 pm

Thanks Dunc!

Ill check out the guy Terry. Ive since found a place in Germany.

They seem to do everything! Expensive though. That wee roller will be about £45 by the time it gets here - https://shop.strato.de/epages/645129...ing=b77+roller

Michael Maurice · 14th Dec 2016, 9:36 pm

You must check the 100nF/275V AC capacitor which is mounted on the voltage selector panel which itself bolted to the mains transformer.

They fail and give off a rather nasty burning plastic smell when they do so.

There is another similar type on the capstan motor speed control board this one is 470nF/275V AC

cliofreak · 14th Dec 2016, 10:42 pm

Thanks Michael!

I've just ordered these two caps based on your recommendation. I'll have the power supply tomorrow or the next day. Cant wait to fire it up and see if its functioning.

Also I've bought a new pinch roller and a few caps. £50 so far.

Anything else I should look out for?

Michael Maurice · 16th Dec 2016, 12:49 am

Look at the pots for adjusting bias, levels and eq and just check that the sliders haven't fallen off.

jblink1 · 16th Dec 2016, 9:21 am

Also check out Nagravox on ebay. Peter has a huge list of spares and advice for all things Revox. The only down side is that he is in Australia so best to combine orders to save postage

cliofreak · 19th Dec 2016, 9:02 pm

Thanks guys.
So Im one step closer as my IEC C9 power cord has arrived so I can turn on the B77 for the first time.

Ok... Well its doing stuff. I can't test tape yet because Im waiting on a new pinch roller but with reels off Im just pressing buttons to see what works.

1. Should the capstan spin constantly (as soon as I power it on)
2. Play and record only stay on when being held (both stop when I take finger off button)
3. The reels seem to be spinning very fast in play/rec modes
4. Variable speed does nothing and tape speed button does nothing I think. Certainly not half the speed.

Its as if its in some sort of 'speed audition tape' mode where you can scrub through the audio.
5. The VU meters are dark so I presume the bulbs are gone.

Any help very much appreciated!
Thanks

Michael Maurice · 19th Dec 2016, 9:44 pm

1: Yes
2: Thats normal, the end of tape detection is doing its job
3: Thats normal, its not the speed but the torque that is reduced in play/rec
4: Varispeed and tape speed affect the speed of the capstan only.
5: Correct

cliofreak · 19th Dec 2016, 11:38 pm

Awesome Michael!!!

Well, this all looks promising. Just waiting for the pinch roller now so I can try it with tape. The capstan is completely coated in the goo from the decomposed pinch roller so I'll have a job cleaning that.

Any ideas what bulbs are in the VU meters?

cliofreak · 19th Dec 2016, 11:51 pm

Never mind!

T5 (W2D 24V 1w)

jamesperrett · 20th Dec 2016, 1:34 pm

Does the capstan change speed when you change the speed switch? You can sometimes hear the motor speeding up or slowing down when you change the switch and you should certainly be able to see the difference in speed with all the goo on the capstan.

cliofreak · 28th Dec 2016, 5:06 pm

Hi,

Yes the capstan is working fine.
Ive just plugged it in after Xmas to see if I can get it working -

So,
1. It 'monitors' the input from the front 1/4 jacks fine. In stereo. Its good!
2. The right VU meter does not match what Im hearing. Its bopping up and down significantly lower than the left VU meter. Needs balanced?

Biggest issue -

3. When I flick to 'tape monitor' when recording, the level is so so so quiet, then when I play back what Ive recorded, it confirms that it is recorded so so so so quiet.

So, what can cause this? Bad tape? Its the old tape that was on the machine.
When I playback some old sessions that are on the tape, it sounds fine.

So is it a rec head issue, an old tape issue or something else? An ideas please

cliofreak · 28th Dec 2016, 5:40 pm

Is there a chance that the tape is back to front or something!?
When I first got the machine, it looked weird. The spool on the left (I think, as I took them off at one point) had the reel looking like it was upside down (I couldn't make it run across the heads with the glossy side touching the head). I ended up cutting the tape and emptying one whole reel so I could wind it in a way that would allow the tape to feed with the glossy side on the heads. At one point I tried recording today and I could hear two separate recordings playing back. My new recording but very very very very quiet and some other old recording.

cliofreak · 28th Dec 2016, 6:06 pm

Sorry to keep adding to this story but developments...

I think the tape is the right way up. Glossy side is definitely touching heads.
I've since discovered, (thanks to the nice feature on the B77) that the left and right channels are actually not as they should be. Im recording a stereo Prophet 08. When I listen to the stereo monitor IN its as if the bass is all in the left and the treble is in the right. When I used the handy function on the B77, I can isolate the left and right and switch them. They are split where bass is in the left and treble in the right. This explains the VU meters not matching. When in MONO, they're fine. Bang on.

So,

1. LR is not combining in stereo as they should...splitting bass and treble
2. Recordings are still very very very very very quiet.

Ah the joys. Thoughts?

cliofreak · 28th Dec 2016, 6:25 pm

Current setup...

John Caswell · 28th Dec 2016, 6:32 pm

Are you absolutely sure you have the tape on the reels correctly, and not inside out, generally the MATT side should be to the heads with the glossy side out.
Try it reversed and see what happens!
I have to admit I have never seen glossy oxide.

John

cliofreak · 28th Dec 2016, 11:11 pm

I've fixed this issue!!

Tape was on correct way.
The heads were disgusting and a good clean with electrical contact cleaner took off lots of rusty coloured dirt. As soon as they dried I tried it and the recording level was almost that of the line in so I guess, its working as it should.

Sometimes when working on problems, different apparent problems appear and they have no relevance to the issue.
This was the case with the left bass/right treble VU meter not reading correctly.
Amazingly, I had the stereo OUTS from the synth coming from two different OUTPUTs (A&B). As soon as both LR were coming from Main Output, the channels were balanced. Stupid but everything is possible in these diagnostic situations.

The pinch wheel needs a washer I think. It needs to be on quite loose otherwise it stalls. I can't believe there isn't a bearing on the roller.

John Caswell · 28th Dec 2016, 11:53 pm

Good work.
One of the main maintenance jobs with any tape machine is to keep the heads, locating surfaces, guides, rollers and pinch wheels squeaky clean, try to clean weekly. When you say electrical contact cleaner I assume something like Isopropanol (IPA) and not something with a lubricant in it.
If you have used the latter clean it all off immediately with IPA or Methylated spirit.
As far as the pinch wheel is concerned, I am sure there are some steel shims and/or teflon washers above and below it. If you have a service manual it will show you what goes where, and if you don't have the necessary parts they are readily available off the web.

John

cliofreak · 29th Dec 2016, 12:05 am

Thanks John,

yeah its like Isopropanol. It evaporates.
There are some teflon washers but to be honest, I can't tighten the screw for the cover of the pinch roller as tight as Id like. Its really loose or it starts to bite. Ill look for a really thin shim washer or the like to get it sorted.

Next thing to do is to try it with my Echomatic DIY Delay/Mixer box that Ive made. When I used this with the Marantz cp430 I modded, I was able to slow the tape right down to a near stop by adding a resister in the form of a 20K pot in the circuitry.

Has anyone ever modded a reel to reel to make the reel come to an almost stop to allow really long delays between play and rec head?

13th Dec 2016, 6:15 pm	#1
cliofreak Retired Dormant Member Join Date: Dec 2016 Location: Derry, Northern Ireland, UK. Posts: 17	ReVox B77 MkII - HELP Hey there, I've acquired a beautiful Revox B77 and I'm determined to get it up and running nicely. 1. I have no power lead yet so don't even know if it will power on. I've one ordered. 2. When I do power it on, I can tell that I'll be doing nothing till I get a new capstan or possibly it's called a 'pressure roller' as the current one is all gummed up! Anyone any ideas on how to get hold of one of these in the UK? Are they a generic fit or do they change size dependant on the machine? Thanks! Attached Thumbnails

13th Dec 2016, 10:37 pm	#2
Dunc100 Retired Dormant Member Join Date: Dec 2016 Location: Driffield, East Riding of Yorkshire, UK. Posts: 19	Re: ReVox B77 MkII - HELP Hi Clio freak, The B77 is a great machine, I'm still waiting for mine. That pinch roller looks nasty and unfortunately I can't suggest anywhere in the UK for a replacement. The rollers are different sizes for different machines so "any old" roller wont do. You'll end up with all sorts of mess going on, tape everywhere or chewed up. No one wants that. There is a service provided by someone in the states who goes by Terry. I think if you Google Terrys rubber rollers he'll be on there. He refurbishes yours then sends you one back. No affiliation and all that but I hear he has a good reputation. I presume you've checked those heads out or it'll be a dear doo. Hope you get her running as well as she is capable as it'll be worth it.

13th Dec 2016, 11:05 pm	#3
cliofreak Retired Dormant Member Join Date: Dec 2016 Location: Derry, Northern Ireland, UK. Posts: 17	Re: ReVox B77 MkII - HELP Thanks Dunc! Ill check out the guy Terry. Ive since found a place in Germany. They seem to do everything! Expensive though. That wee roller will be about £45 by the time it gets here - https://shop.strato.de/epages/645129...ing=b77+roller

14th Dec 2016, 9:36 pm	#4
Michael Maurice Moderator Join Date: Feb 2006 Location: Wembley, Middlesex Posts: 7,224	Re: ReVox B77 MkII - HELP You must check the 100nF/275V AC capacitor which is mounted on the voltage selector panel which itself bolted to the mains transformer. They fail and give off a rather nasty burning plastic smell when they do so. There is another similar type on the capstan motor speed control board this one is 470nF/275V AC __________________ Forum Moderator http://www.michaelmauricerepairs.co.uk/

14th Dec 2016, 10:42 pm	#5
cliofreak Retired Dormant Member Join Date: Dec 2016 Location: Derry, Northern Ireland, UK. Posts: 17	Re: ReVox B77 MkII - HELP Thanks Michael! I've just ordered these two caps based on your recommendation. I'll have the power supply tomorrow or the next day. Cant wait to fire it up and see if its functioning. Also I've bought a new pinch roller and a few caps. £50 so far. Anything else I should look out for?

16th Dec 2016, 12:49 am	#6
Michael Maurice Moderator Join Date: Feb 2006 Location: Wembley, Middlesex Posts: 7,224	Re: ReVox B77 MkII - HELP Look at the pots for adjusting bias, levels and eq and just check that the sliders haven't fallen off. __________________ Forum Moderator http://www.michaelmauricerepairs.co.uk/

16th Dec 2016, 9:21 am	#7
jblink1 Diode Join Date: Nov 2016 Location: Southampton, Hampshire, UK. Posts: 8	Re: ReVox B77 MkII - HELP Also check out Nagravox on ebay. Peter has a huge list of spares and advice for all things Revox. The only down side is that he is in Australia so best to combine orders to save postage

19th Dec 2016, 9:02 pm	#8
cliofreak Retired Dormant Member Join Date: Dec 2016 Location: Derry, Northern Ireland, UK. Posts: 17	Re: ReVox B77 MkII - HELP Thanks guys. So Im one step closer as my IEC C9 power cord has arrived so I can turn on the B77 for the first time. Ok... Well its doing stuff. I can't test tape yet because Im waiting on a new pinch roller but with reels off Im just pressing buttons to see what works. 1. Should the capstan spin constantly (as soon as I power it on) 2. Play and record only stay on when being held (both stop when I take finger off button) 3. The reels seem to be spinning very fast in play/rec modes 4. Variable speed does nothing and tape speed button does nothing I think. Certainly not half the speed. Its as if its in some sort of 'speed audition tape' mode where you can scrub through the audio. 5. The VU meters are dark so I presume the bulbs are gone. Any help very much appreciated! Thanks

19th Dec 2016, 9:44 pm	#9
Michael Maurice Moderator Join Date: Feb 2006 Location: Wembley, Middlesex Posts: 7,224	Re: ReVox B77 MkII - HELP 1: Yes 2: Thats normal, the end of tape detection is doing its job 3: Thats normal, its not the speed but the torque that is reduced in play/rec 4: Varispeed and tape speed affect the speed of the capstan only. 5: Correct __________________ Forum Moderator http://www.michaelmauricerepairs.co.uk/

19th Dec 2016, 11:38 pm	#10
cliofreak Retired Dormant Member Join Date: Dec 2016 Location: Derry, Northern Ireland, UK. Posts: 17	Re: ReVox B77 MkII - HELP Awesome Michael!!! Well, this all looks promising. Just waiting for the pinch roller now so I can try it with tape. The capstan is completely coated in the goo from the decomposed pinch roller so I'll have a job cleaning that. Any ideas what bulbs are in the VU meters?

19th Dec 2016, 11:51 pm	#11
cliofreak Retired Dormant Member Join Date: Dec 2016 Location: Derry, Northern Ireland, UK. Posts: 17	Re: ReVox B77 MkII - HELP Never mind! T5 (W2D 24V 1w)

20th Dec 2016, 1:34 pm	#12
jamesperrett Octode Join Date: May 2007 Location: Liss, Hampshire, UK. Posts: 1,873	Re: ReVox B77 MkII - HELP Does the capstan change speed when you change the speed switch? You can sometimes hear the motor speeding up or slowing down when you change the switch and you should certainly be able to see the difference in speed with all the goo on the capstan.

28th Dec 2016, 5:06 pm	#13
cliofreak Retired Dormant Member Join Date: Dec 2016 Location: Derry, Northern Ireland, UK. Posts: 17	Re: ReVox B77 MkII - HELP Hi, Yes the capstan is working fine. Ive just plugged it in after Xmas to see if I can get it working - So, 1. It 'monitors' the input from the front 1/4 jacks fine. In stereo. Its good! 2. The right VU meter does not match what Im hearing. Its bopping up and down significantly lower than the left VU meter. Needs balanced? Biggest issue - 3. When I flick to 'tape monitor' when recording, the level is so so so quiet, then when I play back what Ive recorded, it confirms that it is recorded so so so so quiet. So, what can cause this? Bad tape? Its the old tape that was on the machine. When I playback some old sessions that are on the tape, it sounds fine. So is it a rec head issue, an old tape issue or something else? An ideas please

28th Dec 2016, 5:40 pm	#14
cliofreak Retired Dormant Member Join Date: Dec 2016 Location: Derry, Northern Ireland, UK. Posts: 17	Re: ReVox B77 MkII - HELP Is there a chance that the tape is back to front or something!? When I first got the machine, it looked weird. The spool on the left (I think, as I took them off at one point) had the reel looking like it was upside down (I couldn't make it run across the heads with the glossy side touching the head). I ended up cutting the tape and emptying one whole reel so I could wind it in a way that would allow the tape to feed with the glossy side on the heads. At one point I tried recording today and I could hear two separate recordings playing back. My new recording but very very very very quiet and some other old recording.

28th Dec 2016, 6:06 pm	#15
cliofreak Retired Dormant Member Join Date: Dec 2016 Location: Derry, Northern Ireland, UK. Posts: 17	Re: ReVox B77 MkII - HELP Sorry to keep adding to this story but developments... I think the tape is the right way up. Glossy side is definitely touching heads. I've since discovered, (thanks to the nice feature on the B77) that the left and right channels are actually not as they should be. Im recording a stereo Prophet 08. When I listen to the stereo monitor IN its as if the bass is all in the left and the treble is in the right. When I used the handy function on the B77, I can isolate the left and right and switch them. They are split where bass is in the left and treble in the right. This explains the VU meters not matching. When in MONO, they're fine. Bang on. So, 1. LR is not combining in stereo as they should...splitting bass and treble 2. Recordings are still very very very very very quiet. Ah the joys. Thoughts?

28th Dec 2016, 6:25 pm	#16
cliofreak Retired Dormant Member Join Date: Dec 2016 Location: Derry, Northern Ireland, UK. Posts: 17	Re: ReVox B77 MkII - HELP Current setup... Attached Thumbnails

28th Dec 2016, 6:32 pm	#17
John Caswell Hexode Join Date: Jul 2009 Location: Wokingham, Berkshire, UK. Posts: 437	Re: ReVox B77 MkII - HELP Are you absolutely sure you have the tape on the reels correctly, and not inside out, generally the MATT side should be to the heads with the glossy side out. Try it reversed and see what happens! I have to admit I have never seen glossy oxide. John

28th Dec 2016, 11:11 pm	#18
cliofreak Retired Dormant Member Join Date: Dec 2016 Location: Derry, Northern Ireland, UK. Posts: 17	Re: ReVox B77 MkII - HELP I've fixed this issue!! Tape was on correct way. The heads were disgusting and a good clean with electrical contact cleaner took off lots of rusty coloured dirt. As soon as they dried I tried it and the recording level was almost that of the line in so I guess, its working as it should. Sometimes when working on problems, different apparent problems appear and they have no relevance to the issue. This was the case with the left bass/right treble VU meter not reading correctly. Amazingly, I had the stereo OUTS from the synth coming from two different OUTPUTs (A&B). As soon as both LR were coming from Main Output, the channels were balanced. Stupid but everything is possible in these diagnostic situations. The pinch wheel needs a washer I think. It needs to be on quite loose otherwise it stalls. I can't believe there isn't a bearing on the roller.

28th Dec 2016, 11:53 pm	#19
John Caswell Hexode Join Date: Jul 2009 Location: Wokingham, Berkshire, UK. Posts: 437	Re: ReVox B77 MkII - HELP Good work. One of the main maintenance jobs with any tape machine is to keep the heads, locating surfaces, guides, rollers and pinch wheels squeaky clean, try to clean weekly. When you say electrical contact cleaner I assume something like Isopropanol (IPA) and not something with a lubricant in it. If you have used the latter clean it all off immediately with IPA or Methylated spirit. As far as the pinch wheel is concerned, I am sure there are some steel shims and/or teflon washers above and below it. If you have a service manual it will show you what goes where, and if you don't have the necessary parts they are readily available off the web. John

29th Dec 2016, 12:05 am	#20
cliofreak Retired Dormant Member Join Date: Dec 2016 Location: Derry, Northern Ireland, UK. Posts: 17	Re: ReVox B77 MkII - HELP Thanks John, yeah its like Isopropanol. It evaporates. There are some teflon washers but to be honest, I can't tighten the screw for the cover of the pinch roller as tight as Id like. Its really loose or it starts to bite. Ill look for a really thin shim washer or the like to get it sorted. Next thing to do is to try it with my Echomatic DIY Delay/Mixer box that Ive made. When I used this with the Marantz cp430 I modded, I was able to slow the tape right down to a near stop by adding a resister in the form of a 20K pot in the circuitry. Has anyone ever modded a reel to reel to make the reel come to an almost stop to allow really long delays between play and rec head?