Ferrograph 7, not working on right channel - UK Vintage Radio Repair and Restoration Discussion Forum

pecbtandberg · 14th Feb 2012, 12:31 am

I was fortunate to have one of these given to me the other week. The previous owner didn't feel like doing the work it might need to get it running again. The usual items, pinch roller and idlers had to be replaced. After doing that, I found that there was no output from the right channel (4 track stereo model, type 2 with dolby).
VU meters show nothing on record or playback. DC fuse is OK for the right channel. There was some crackle on both channels at first, left one settled down and is now OK but not the right channel. Am I right in assuming the crackling could be sign of failed/failing caps.
Any pointers any one and has anyone got a full serice manual or copy for this machine please. Found a incomplete copy at www.morphet.org.uk but it's not very clear.

SteveCG · 14th Feb 2012, 6:58 pm

Just to confirm: Is your model a 704D? IE - no built in audio power amplifiers.

The slide switches on these Ferrographs are notorious for bad/no contacts. If you set them to 'source' and give the tape-recorder an input then do you hear anything on the outputs, either the low-level O/P or the line O/P?

Don't forget that the Ferrograph rotary controls are not ganged together, so the left and right channels require separate adjustment.

pecbtandberg · 14th Feb 2012, 10:24 pm

This model has got built amps. I know about the controls being seperate for left and right channels. No, there is no response from meters on record or playback. After recording on this machine and testing the tape on another deck, there is no evidence of any recording on the right channel. It's as if the dc fuse had gone on the right channel but it hasn't.

SteveCG · 15th Feb 2012, 11:45 am

I understand what you say about no meter deflection and nothing on the tape on the right hand channel. Are you saying that the recorder does work on the LHS, but there is no record or replay meter deflection on either channel? Have you set the machine for stereo recording (the switch between and just below the meters)?

However it should be possible to check that audio signals are getting through parts of the Ferrograph by connecting an input to both the left and the right channels and then listening on both the left and right 600 Ohm line level outputs. Set the output slide switches to Input - not Tape - and let us know what you hear.

pecbtandberg · 15th Feb 2012, 10:24 pm

Left channel is OK. Recording/playback and vu meters. Right channel no output on the 600 ohm sockets. Nothing records on right channel. No audio going through on right channel. No vu meter activity on record or playback on right channel. I am experienced at using decks, so it's not a problem due to switch/control settings etc. There is momentary crackling from the right speaker when the tape/source switch is activated back and forth. I have to admit that as yet, I've not had chance to give all the switches a good dose of electrical contact cleaner yet. Trying to get a few pointers for next week as I'll not be at work that week.

SteveCG · 16th Feb 2012, 7:17 pm

Further ideas:

1) When in stereo record mode, and with the meters switched to reading 'bias', do you get a reading on the RHS meter?

2) I assume you have a Series 7 Dolby machine (8.25 inch max spool size). However the circuitry is very similar to that of the Logic 7 Dolby. This can also be found on the morphet web site you have already mentioned.

3) The fact you hear some crackling when you operate the RHS Source switch implies that the later parts of the RHS audio chain may be working. A 'crackling' slide switch is typical of the types used by Ferrograph at their age of 40 odd years.

pecbtandberg · 16th Feb 2012, 11:24 pm

Sorry if I'm a bit slow getting back to you. I work a double shift one week and then have a week off. This is my working week. I had downloaded the logic 7 files as you suggested, as I thought it was similar to mine. I'll try the bias test when I get chance. I'm wondering if it's the switch as well. I was getting no output from the left channel at first when I tried the deck but it worked after moving the switch back and forth a few times. I'll see if I can give them both a clean with some contact cleaner.

BillDWVA · 17th Feb 2012, 3:36 pm

The way I traced a faulty amplifier on a Series 7 was to use a simple battery powered audio amplifier as a 'trace' amp coupled via a capacitor (to isolate any DC) and, using the circuit diagram I traced the audio at various points through the transistor stages whilst the machine was playing back a tape recorded on another machine and/or with a signal source connected to a line input. Found the break quite quickly this way.
On this machine I found the tantalum capacitor(s) (C216 and C301) were leaky.

Hope this helps, Bill

pecbtandberg · 18th Feb 2012, 2:46 am

Thanks for the suggestions. The problem is not just the playback amp, it's on the record side as well. The right channel is dead for any signal, in or out. Suggests to me a break early on or the record/playback switch is doing nothing.

14th Feb 2012, 12:31 am	#1
pecbtandberg Retired Dormant Member Join Date: Oct 2011 Location: Buxton Posts: 15	Ferrograph 7, not working on right channel I was fortunate to have one of these given to me the other week. The previous owner didn't feel like doing the work it might need to get it running again. The usual items, pinch roller and idlers had to be replaced. After doing that, I found that there was no output from the right channel (4 track stereo model, type 2 with dolby). VU meters show nothing on record or playback. DC fuse is OK for the right channel. There was some crackle on both channels at first, left one settled down and is now OK but not the right channel. Am I right in assuming the crackling could be sign of failed/failing caps. Any pointers any one and has anyone got a full serice manual or copy for this machine please. Found a incomplete copy at www.morphet.org.uk but it's not very clear.

14th Feb 2012, 6:58 pm	#2
SteveCG Nonode Join Date: Jun 2009 Location: Herefordshire, UK. Posts: 2,495	Re: Ferrograph 7, not working on right channel Just to confirm: Is your model a 704D? IE - no built in audio power amplifiers. The slide switches on these Ferrographs are notorious for bad/no contacts. If you set them to 'source' and give the tape-recorder an input then do you hear anything on the outputs, either the low-level O/P or the line O/P? Don't forget that the Ferrograph rotary controls are not ganged together, so the left and right channels require separate adjustment.

14th Feb 2012, 10:24 pm	#3
pecbtandberg Retired Dormant Member Join Date: Oct 2011 Location: Buxton Posts: 15	Re: Ferrograph 7, not working on right channel This model has got built amps. I know about the controls being seperate for left and right channels. No, there is no response from meters on record or playback. After recording on this machine and testing the tape on another deck, there is no evidence of any recording on the right channel. It's as if the dc fuse had gone on the right channel but it hasn't.

15th Feb 2012, 11:45 am	#4
SteveCG Nonode Join Date: Jun 2009 Location: Herefordshire, UK. Posts: 2,495	Re: Ferrograph 7, not working on right channel I understand what you say about no meter deflection and nothing on the tape on the right hand channel. Are you saying that the recorder does work on the LHS, but there is no record or replay meter deflection on either channel? Have you set the machine for stereo recording (the switch between and just below the meters)? However it should be possible to check that audio signals are getting through parts of the Ferrograph by connecting an input to both the left and the right channels and then listening on both the left and right 600 Ohm line level outputs. Set the output slide switches to Input - not Tape - and let us know what you hear.

15th Feb 2012, 10:24 pm	#5
pecbtandberg Retired Dormant Member Join Date: Oct 2011 Location: Buxton Posts: 15	Re: Ferrograph 7, not working on right channel Left channel is OK. Recording/playback and vu meters. Right channel no output on the 600 ohm sockets. Nothing records on right channel. No audio going through on right channel. No vu meter activity on record or playback on right channel. I am experienced at using decks, so it's not a problem due to switch/control settings etc. There is momentary crackling from the right speaker when the tape/source switch is activated back and forth. I have to admit that as yet, I've not had chance to give all the switches a good dose of electrical contact cleaner yet. Trying to get a few pointers for next week as I'll not be at work that week.

16th Feb 2012, 7:17 pm	#6
SteveCG Nonode Join Date: Jun 2009 Location: Herefordshire, UK. Posts: 2,495	Re: Ferrograph 7, not working on right channel Further ideas: 1) When in stereo record mode, and with the meters switched to reading 'bias', do you get a reading on the RHS meter? 2) I assume you have a Series 7 Dolby machine (8.25 inch max spool size). However the circuitry is very similar to that of the Logic 7 Dolby. This can also be found on the morphet web site you have already mentioned. 3) The fact you hear some crackling when you operate the RHS Source switch implies that the later parts of the RHS audio chain may be working. A 'crackling' slide switch is typical of the types used by Ferrograph at their age of 40 odd years.

16th Feb 2012, 11:24 pm	#7
pecbtandberg Retired Dormant Member Join Date: Oct 2011 Location: Buxton Posts: 15	Re: Ferrograph 7, not working on right channel Sorry if I'm a bit slow getting back to you. I work a double shift one week and then have a week off. This is my working week. I had downloaded the logic 7 files as you suggested, as I thought it was similar to mine. I'll try the bias test when I get chance. I'm wondering if it's the switch as well. I was getting no output from the left channel at first when I tried the deck but it worked after moving the switch back and forth a few times. I'll see if I can give them both a clean with some contact cleaner.

17th Feb 2012, 3:36 pm	#8
BillDWVA Pentode Join Date: Nov 2010 Location: Tenby, Pembrokeshire, Wales, UK. Posts: 139	Re: Ferrograph 7, not working on right channel The way I traced a faulty amplifier on a Series 7 was to use a simple battery powered audio amplifier as a 'trace' amp coupled via a capacitor (to isolate any DC) and, using the circuit diagram I traced the audio at various points through the transistor stages whilst the machine was playing back a tape recorded on another machine and/or with a signal source connected to a line input. Found the break quite quickly this way. On this machine I found the tantalum capacitor(s) (C216 and C301) were leaky. Hope this helps, Bill

18th Feb 2012, 2:46 am	#9
pecbtandberg Retired Dormant Member Join Date: Oct 2011 Location: Buxton Posts: 15	Re: Ferrograph 7, not working on right channel Thanks for the suggestions. The problem is not just the playback amp, it's on the record side as well. The right channel is dead for any signal, in or out. Suggests to me a break early on or the record/playback switch is doing nothing.