B-77 not erasing or recording (sorry English)

[Ken]

Hello everyone,

I am very, very sorry, I do not speak German so I cannot search your forum for an answer. Would someone please help me in English.

I have a B-77 that has just stopped recording and erasing. The red record lights both come on and the input signal is monitored correctly in 'monitor' switch position and is passing through the machine but it is not recorded to tape. In the 'tape' monitor switch position (whilst recording) all I get is the existing recording.

I have a spare 'record amplifier pcb' which I have tried, but it did not help. I have a few other spare pcb's and parts, but these are for a slow speed B77.

I am in Spain and have no repair shops that understand Revox and shipping cost to Germany is probably more than the machines value. Could anyone please tell me if it sounds like something minor or is my B77 at the end of it's life.

Thank you very much for any advice.
Ken.

[Niederberger Jean]

AW: B-77 not erasing or recording (sorry English)

ciao
first of all, wellcome on the Revox Forum. I think your recorder is reproducing well when you insert an already recorded tape??? In my opinion (but there may be different kind of problems) there could also only be a problem of dust on the earising head (the first of the three heads... also clean this earising head with a liquid called "Isoproponol" (you should find this alcohol liquid in a chemistry shop) and repeat this proceedure of cleaing several times in order to clean proper and completly free of dust such earising head and also the other two heads with a clean towel and give attention that no liquid may enter in the cabestan (which is on the right of the reproducing head).
Some of old tapes may cover the heads and the earising head ist the first one with a nasti dust.
Buena suerte !

[Ken]

AW: B-77 not erasing or recording (sorry English)

Hello Niederberger Jean,

Thank you very much for your reply.

Yes it does play existing recording tapes ok. It just will not erase or record over an old tape or even record on a new tape.

I have already thoroughly cleaned all of the heads and de-magnetised them. No luck with that.

It seems as though the 'record/erase' signals are not being sent to the heads. I have looked at the service manual and (I'm not a technician) it looks as though the oscillator pcb swithes these signals, but I am not knowledgable enough to know if this is the problem or (hoping) there is something simple.

Thank you again for replying and the welcome.
Ken.

[heinz]

AW: B-77 not erasing or recording (sorry English)

Good evening Ken,
my B77 from the year 1980 sometimes shows the same strange behaviour like your B77.
Luckily it is only a case of bad contact. Sometimes it does not record at all,
sometimes only on one channel, and sometimes on both channels, but in mono.
I solve the problem by starting a test- recording on both channels and listening to the result. In case of a faulty recording I operate the switches 'Rec L, Rec R and Monitor' again and again while the tape ist running, and up to now this has always been helpful. But sometimes it requires some patience and a lot of switching until the recording eventually is alright. Maybe you can try this procedure with your B77 ? Bad contacts very often seem to be the cause of
trouble with the B77, but still it's my favourite tape - recorder.
I hope that your B77 is not defective but only suffering from rusty and dusty contacts like mine.
With kind regards
Heinz

[Ken]

AW: B-77 not erasing or recording (sorry English)

Hello Heinz,

It is very nice of you all to help me... thank you.

I have been experimenting a bit more and unfortunately it is not a case of bad contacts (I wish it was). I do 'maintenance' clean the machine regularly, even all of the interconnect pcb switch contacts etc.

I think I have discovered that it is definately the oscillator pcb. I have swapped it with an old spare I have and with that the erase and record now function properly. I think it is possibly the triac or a capacitor component.

That may sound like good news, but... all of the bias trim pots are on this pcb and I have absolutely no equipment to adjust them. I think it needs tone generators, oscilliscope and tone tapes... I have none of these

I wonder if I can ask if you or anyone knows if I can make the adjustments without the equipment ?

Thank you again,
Ken.

[namenloser benutzer]

AW: B-77 not erasing or recording (sorry English)

Hello Ken,

if you have no measuring equipment, my suggestion for you would be to use the audiotester.
Audiotester 1.4 is available as shareware from http://www.pcfreunde.de/download/det...diotester.html

This is a set of virtual instruments (audiofrequency oscillator, spectrum analyser and scope) using the soundcard and the computing power of your PC.
I have tried a couple of these programs, some were not stable.
I consider the audiotester as audiofrequency oscillator and spectrum analyser as very useful and stable with Win95/ME/XP Home.
The bias and level adjustments for a nearly perfect setup using your prefered tape material can be done with this tool.

For more information please ask

[Ken]

AW: B-77 not erasing or recording (sorry English)

Hello pausenprofi,

Thank you very much for the reply, information and link to the software.

I have downloaded and installed the Audio Tester and I have read through the programs help topics. To be very honest, I am totally lost on how to use Audio Tester.

I do have the Revox service manual on CD, I also have some new Quantegy 456 tapes. I have some good quality interconnect cables, but assume I might need some phono-jack converters to go into my PC connections (running Win XP). So hopefully I can get everything connected.

My B-77 is a 2 track, 3 3/4 - 7 1/2 ips connected to a Revox B-750 amp.

If you have the time, any advice on how to do the adjustments using Audio Tester would be appreciated.

Thank you very much for your interest in my thread and problem.

Ken.

[namenloser benutzer]

AW: B-77 not erasing or recording (sorry English)

Hello Ken,

The first step is to become familiar with this software.
oscillator (frequenzgenerator) seems to be easy to understand.

(In this space I wanted to place a picture of the audiotester table, but this thread only takes fotos from the web.)

In this table select the required waveform e.g. sin for sinus.
Modify the frequency in display or using the up/down arrows.
L dig R select the attenuation of the wave-output signal.
Start the output usings start button.
In you have a speaker on this line-out you can now hear the generated sound.
Play with this tool to become sure in using it.

The spectrum analyser is the receiver. It would be best if you connect for example the left output of your soundcard to the left input (line-in).
To make the input-waveform visible select the parameters on the spectrum analyser as depicted:

(another picture)

If you need more information and want to see the tables it would be best if you gave me your e-mail address for further communication.

Greetings
pausenprofi

[Ken]

AW: B-77 not erasing or recording (sorry English)

Hello pausenprofi,

Thanks again for the further information.

I have been looking at the Audio Tester software and I have to be honest, it has completely stumped me.

I do truly appreciate your help, but I think it is too much to ask of you to explain it all to me and I would feel very guilty for asking.

If you have some simple drawings that do not require you to spend a lot of time on this my e-mail is... ken @ inmo-michaela.com (minus spaces). Other than that, I will try to find a good sound engineer in my area, but Revox was never really common in Spain.

Thank you again and everyone who has taken an interest in my thread... excellent forums and very nice members.

Ken.