Sony BVW-75P - UK Vintage Radio Repair and Restoration Discussion Forum

Satski66 · 20th Jan 2024, 11:18 pm

Hi have a wonderful old edit machine that has developed a strange fault.
Whilst viewing a tape the picture became blocky and then failed altogether although the TCR data is still visable.

I looked at the obvious suspects, tape heads, capacitors, etc but nothing seemed amiss. The heads were cleaned but no resolve.

I did replace the main TBU board and this did resolve the issue for a few minutes but then the same problem returned which effectively rules out a TBU fault?

I can confirm that when the composite input is fed with colour bars, I can see the output which suggests that it is from the playback circuit??

Any suggestions?

HurtyAC · 21st Jan 2024, 9:21 am

If the machine was used in a warm environment the cream glue used to secure wires on the back of the boards goes a dark brown and becomes conductive. To remove it you just press down on it with the edge of a screw diver and it pings off. I need a photo of the back of the boards like the timebase one. The same happens with the metal box filters. These would have to be removed off the board and then you will see a bit of insulation board underneath secured with the same glue, again has to be removed. The filters are active. BUT I need more information first!! Photos of the back of the boards first. Do you have an Oscilloscope? and do you know how to use one? You will need this to repair these.

Satski66 · 21st Jan 2024, 7:52 pm

Hi

There are several TBC boards on this machine. Do you want photos of them all. I assume that you want photos of the board side rather then the component side?

Yes I have a scope and yes I know how to drive this.

Just to mention that the machine is in a cooler environment at the moment but the normal working environment is warm.

20th Jan 2024, 11:18 pm	#1
Satski66 Diode Join Date: Jan 2024 Location: Derby, Derbyshire, UK. Posts: 2	Sony BVW-75P Hi have a wonderful old edit machine that has developed a strange fault. Whilst viewing a tape the picture became blocky and then failed altogether although the TCR data is still visable. I looked at the obvious suspects, tape heads, capacitors, etc but nothing seemed amiss. The heads were cleaned but no resolve. I did replace the main TBU board and this did resolve the issue for a few minutes but then the same problem returned which effectively rules out a TBU fault? I can confirm that when the composite input is fed with colour bars, I can see the output which suggests that it is from the playback circuit?? Any suggestions?

21st Jan 2024, 9:21 am	#2
HurtyAC Tetrode Join Date: May 2009 Location: Ware, Hertfordshire, UK. Posts: 75	Re: Sony BVW-75P If the machine was used in a warm environment the cream glue used to secure wires on the back of the boards goes a dark brown and becomes conductive. To remove it you just press down on it with the edge of a screw diver and it pings off. I need a photo of the back of the boards like the timebase one. The same happens with the metal box filters. These would have to be removed off the board and then you will see a bit of insulation board underneath secured with the same glue, again has to be removed. The filters are active. BUT I need more information first!! Photos of the back of the boards first. Do you have an Oscilloscope? and do you know how to use one? You will need this to repair these.

21st Jan 2024, 7:52 pm	#3
Satski66 Diode Join Date: Jan 2024 Location: Derby, Derbyshire, UK. Posts: 2	Re: Sony BVW-75P Hi There are several TBC boards on this machine. Do you want photos of them all. I assume that you want photos of the board side rather then the component side? Yes I have a scope and yes I know how to drive this. Just to mention that the machine is in a cooler environment at the moment but the normal working environment is warm.