Betamax recording - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

Refugee · 2nd Jul 2021, 8:49 pm

We need to look at the circuit diagram to see if the input to the UHF modulator is in parallel with the DIN socket.
Another way to test for this is to try a DIN to 4 phono plug cable.
I reckon the audio is hard wiring itself to the UHF modulator leaving the input open circuit so that it is getting only a faint signal from being right next to it.

simpsons · 3rd Jul 2021, 10:11 am

All sounds a little "hit- and-miss" to me, no pun intended.

Clansman, why not download the "Instruction Manual" for this machine. It's FOC and explains just what you are able to do and the connections to do it.

You will find the Australian version is the one on the web. So, note, when the user guide speaks of the RF converter outputting on channel 2 or 4, this is because down under VHF channels were in use. Your machine RF converter is made for UHF channels used over here and should be left alone. Otherwise everything else is correct for what you need to know.

Chris

gallowfields · 3rd Jul 2021, 1:59 pm

if it plays sound and picture o/k from the dvd through the sanyo to the tv then all the connections are o/k [not mentioned in your first post]. so it appears the vcr is not recording audio as previously mentioned by other members. first thing to try is clening the record /playback switch and then look at the audio bias oscillator .but personally never had that with those machines .

simpsons · 3rd Jul 2021, 11:57 pm

Hmm. I'm not the sharpest tool in the box, but why would a lack of HF/AC bias to the recording head stop the machine from recording the linear sound track?

AC bias, used to reduce distortion when recording audio onto tape, is not used in DC erase low cost audio recorders or those when a magnet is "swung into place" to perform this task.

Before recommending spraying switch cleaner to one of a number of locations, it should be noted that in e-e mode, sound is there. This is a clue.

As Clansman is not confident in servicing this recorder, which I fully respect, I would limit fault finding to what is possible in his circumstances.

Chris

gallowfields · 4th Jul 2021, 4:54 pm

if you do not feel confident about cleaning the record playback switch first ,then you could try operating the record/playback function keys a few times and then check see if it records audio . this is very common in audio recorders and early vhs and beta vcr,s .brian

agardiner · 5th Jul 2021, 2:55 pm

Cleaning is always a good idea, but not sure it will help here given that the unit plays back other tapes OK.

'Magnets' applied in low cost recorders are only there as a cheap way to erase the tape and indeed they cause more noise. However, AC bias is still needed on the recording head to actually record the information. If the oscillator has stopped in the audio recording circuit then this would cause the noted problem.

2nd Jul 2021, 8:49 pm	#21
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,554	Re: Betamax recording We need to look at the circuit diagram to see if the input to the UHF modulator is in parallel with the DIN socket. Another way to test for this is to try a DIN to 4 phono plug cable. I reckon the audio is hard wiring itself to the UHF modulator leaving the input open circuit so that it is getting only a faint signal from being right next to it.

3rd Jul 2021, 10:11 am	#22
simpsons Octode Join Date: Feb 2007 Location: Harrow, London, UK. Posts: 1,493	Re: Betamax recording All sounds a little "hit- and-miss" to me, no pun intended. Clansman, why not download the "Instruction Manual" for this machine. It's FOC and explains just what you are able to do and the connections to do it. You will find the Australian version is the one on the web. So, note, when the user guide speaks of the RF converter outputting on channel 2 or 4, this is because down under VHF channels were in use. Your machine RF converter is made for UHF channels used over here and should be left alone. Otherwise everything else is correct for what you need to know. Chris

3rd Jul 2021, 1:59 pm	#23
gallowfields Hexode Join Date: Feb 2018 Location: Durham, County Durham, UK. Posts: 325	Re: Betamax recording if it plays sound and picture o/k from the dvd through the sanyo to the tv then all the connections are o/k [not mentioned in your first post]. so it appears the vcr is not recording audio as previously mentioned by other members. first thing to try is clening the record /playback switch and then look at the audio bias oscillator .but personally never had that with those machines .

3rd Jul 2021, 11:57 pm	#24
simpsons Octode Join Date: Feb 2007 Location: Harrow, London, UK. Posts: 1,493	Re: Betamax recording Hmm. I'm not the sharpest tool in the box, but why would a lack of HF/AC bias to the recording head stop the machine from recording the linear sound track? AC bias, used to reduce distortion when recording audio onto tape, is not used in DC erase low cost audio recorders or those when a magnet is "swung into place" to perform this task. Before recommending spraying switch cleaner to one of a number of locations, it should be noted that in e-e mode, sound is there. This is a clue. As Clansman is not confident in servicing this recorder, which I fully respect, I would limit fault finding to what is possible in his circumstances. Chris

4th Jul 2021, 4:54 pm	#25
gallowfields Hexode Join Date: Feb 2018 Location: Durham, County Durham, UK. Posts: 325	Re: Betamax recording if you do not feel confident about cleaning the record playback switch first ,then you could try operating the record/playback function keys a few times and then check see if it records audio . this is very common in audio recorders and early vhs and beta vcr,s .brian

5th Jul 2021, 2:55 pm	#26
agardiner Octode Join Date: Sep 2020 Location: Thetford, Norfolk, UK. Posts: 1,743	Re: Betamax recording Cleaning is always a good idea, but not sure it will help here given that the unit plays back other tapes OK. 'Magnets' applied in low cost recorders are only there as a cheap way to erase the tape and indeed they cause more noise. However, AC bias is still needed on the recording head to actually record the information. If the oscillator has stopped in the audio recording circuit then this would cause the noted problem.