Another Watkins Copicat problem - UK Vintage Radio Repair and Restoration Discussion Forum

The Sadows · 8th Mar 2016, 1:05 pm

Hi all

I have a solid state Copicat, Mk3 or 4 I believe, which was working when stored about 10 years ago but since taking out of storage and testing, there is no recorded echo.

I have tapped the record heads and hear the pop from my amp.
If I increase the Sustain, I get the 'Telstar' feedback effect.
If I increase the Swell I can hear the tape passing the playback heads with increasing volume.
Pressing the playback head switches gives the correct noise delay but no guitar sound at all just the clean passthrougn guitar sound.
I have measured the record head resistance with a digital meter - 74 Ohms.
I have fitted a home made tape loop from a reel I have for my Akai reel to reel machine.

Having recently retired, I am keen to develop my Hank skills so would like to get this machine working if possible. Otherwise its EFTP I suppose.

Any advice gratefully received...

Many thanks, Andy.

ITAM805 · 8th Mar 2016, 3:02 pm

Hi Andy

as the 'repro' side seems to be working, then it's either in the input or mixing stage ? Do you get any sound when plugged into the inputs ?

vidjoman · 8th Mar 2016, 3:48 pm

Could be just dirty switches that need cleaning after being unused for 10 years.

The Sadows · 8th Mar 2016, 4:50 pm

Quote:

Originally Posted by ITAM805

Do you get any sound when plugged into the inputs ?

Thanks for the quick response - Yes I can play the guitar clean, both channel gain pots work OK - The 3 head switches are working OK, if I increase the swell or echo volume, I can hear noise (not guitar sounds) which changes as I depress each button.
I can hear the clean guitar at all times, just not the echo effect ... I thought the record head may be open circuit but this gives a reading of around 74 Ohms

The foot switch is also OK.

Andy

ITAM805 · 8th Mar 2016, 6:40 pm

I would guess that there's no signal getting to the record head, or possibly no bias, although you'd usually hear something albeit very distorted. Check obvious things like broken wires to the rec head and so on.

Otherwise you're going to need a schematic and have poke around inside. A scope would be very useful too.

rtbcomp · 9th Mar 2016, 3:21 pm

You haven't got the tape loop inside out have you?

The Sadows · 9th Mar 2016, 10:21 pm

I thought about that one so tried both ways with no difference.

julie_m · 10th Mar 2016, 12:28 am

What happens if you run a length of pre-recorded tape past the Copicat heads? (You might need to record something on all 4 tracks, depending where the head gaps on the Copicat machine are). And what happens if you undo the splice and try to listen to the tape?

Give all the switches and potentiometers a good dose of Servisol and several operations.

The Sadows · 16th Mar 2016, 2:45 pm

If you mean run a tape loop with a pre-recorded signal, the erase head will remove the signal unless I somehow raise the tape away from the erase head surface. I am fairly certain the switches and pots are working correctly but no harm in giving them a squirt or TWO.

Thanks for the suggestions, Andy

Pitchfork · 19th Mar 2016, 12:56 pm

http://wem-owners.com/links-contacts/contacts/

McMurdo · 19th Mar 2016, 2:37 pm

the last solid state copicat I had brought o me was the same; working when put away, not working when brought out. In this case it was pots so dirty they were open circuit. However I also had one with a short circuit electrolytic in there which had internally corroded in storage.

julie_m · 19th Mar 2016, 3:54 pm

Can you get a wiring diagram (which may even have some voltages marked on it, if you're lucky) or at least partly reverse-engineer the circuit? Have you access to an oscilloscope? You really need to be able to follow an audio signal right through the circuit, and see where it is going missing.

A piece of thin card or plastic should be enough to block the field from the erase head, by the way.

Pitchfork · 20th Mar 2016, 12:57 pm

I suggest that it need a service which will sort it out & have an earthed mains lead fitted at same time. I can do this for you rather than you trying to sort it yourself. Home made tape loops from old tape is not a good idea as if it is long-play it will be too thin. Refer to Wem owners link 2 posts ago for contact details

Diabolical Artificer · 21st Mar 2016, 6:09 am

Schematics here http://www.vintagehofner.co.uk/brita...s/wemwire.html
to find out which version you have see here
http://www.vintagehofner.co.uk/brita...s/copicat.html

Andy.

boxdoctor · 22nd Mar 2016, 2:42 pm

Failure of the bias oscillator was one of the main problems I experienced with this model. Usually just the two transistors going o\c. Yours suggests a problem in the record head amplifier circuit. I would, after ensuring that all pots and switches are really clean, replace all the small electrolytic caps, as these dry out, and after a long period of idleness may be completely open circuit.
I've got one of these Mk4s myself, and it is reliable, presumably because it gets fairly regular use. Tony

The Sadows · 9th May 2016, 5:50 pm

Apologies for the long delay between posts. House refurbishment took priority. Thanks for all your suggestions. I do not have an oscilloscope so will have to rely on other forms of diagnostics, one being component substitution. Forgive my lack of electronic knowledge but are the record and playback heads the same? i.e. could I replace the record head with one of the playback heads?

Thanks, Andy

Pitchfork · 13th May 2016, 5:33 pm

The record & playback heads are the same but it may not be a head problem at all, but either an oscillator issue, a recording amp or the recovery circuit.
Get it over to me to sort out I'm near Basingstoke - use a Courier it will cost <£8 to ship across, I fix these all of the time

8th Mar 2016, 1:05 pm	#1
The Sadows Retired Dormant Member Join Date: Mar 2016 Location: Isle of Wight, UK. Posts: 5	Another Watkins Copicat problem Hi all I have a solid state Copicat, Mk3 or 4 I believe, which was working when stored about 10 years ago but since taking out of storage and testing, there is no recorded echo. I have tapped the record heads and hear the pop from my amp. If I increase the Sustain, I get the 'Telstar' feedback effect. If I increase the Swell I can hear the tape passing the playback heads with increasing volume. Pressing the playback head switches gives the correct noise delay but no guitar sound at all just the clean passthrougn guitar sound. I have measured the record head resistance with a digital meter - 74 Ohms. I have fitted a home made tape loop from a reel I have for my Akai reel to reel machine. Having recently retired, I am keen to develop my Hank skills so would like to get this machine working if possible. Otherwise its EFTP I suppose. Any advice gratefully received... Many thanks, Andy.

8th Mar 2016, 3:02 pm	#2
ITAM805 Nonode Join Date: Jul 2010 Location: Folkestone, Kent, UK. Posts: 2,172	Re: Another Watkins Copicat problem Hi Andy as the 'repro' side seems to be working, then it's either in the input or mixing stage ? Do you get any sound when plugged into the inputs ?

8th Mar 2016, 3:48 pm	#3
vidjoman Dekatron Join Date: Jun 2013 Location: East Sussex, UK. Posts: 3,326	Re: Another Watkins Copicat problem Could be just dirty switches that need cleaning after being unused for 10 years.

8th Mar 2016, 6:40 pm	#5
ITAM805 Nonode Join Date: Jul 2010 Location: Folkestone, Kent, UK. Posts: 2,172	Re: Another Watkins Copicat problem I would guess that there's no signal getting to the record head, or possibly no bias, although you'd usually hear something albeit very distorted. Check obvious things like broken wires to the rec head and so on. Otherwise you're going to need a schematic and have poke around inside. A scope would be very useful too.

9th Mar 2016, 3:21 pm	#6
rtbcomp Tetrode Join Date: Aug 2007 Location: Sheffield, South Yorkshire, UK. Posts: 50	Re: Another Watkins Copicat problem You haven't got the tape loop inside out have you?

9th Mar 2016, 10:21 pm	#7
The Sadows Retired Dormant Member Join Date: Mar 2016 Location: Isle of Wight, UK. Posts: 5	Re: Another Watkins Copicat problem I thought about that one so tried both ways with no difference.

10th Mar 2016, 12:28 am	#8
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: Another Watkins Copicat problem What happens if you run a length of pre-recorded tape past the Copicat heads? (You might need to record something on all 4 tracks, depending where the head gaps on the Copicat machine are). And what happens if you undo the splice and try to listen to the tape? Give all the switches and potentiometers a good dose of Servisol and several operations. __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.

16th Mar 2016, 2:45 pm	#9
The Sadows Retired Dormant Member Join Date: Mar 2016 Location: Isle of Wight, UK. Posts: 5	Re: Another Watkins Copicat problem If you mean run a tape loop with a pre-recorded signal, the erase head will remove the signal unless I somehow raise the tape away from the erase head surface. I am fairly certain the switches and pots are working correctly but no harm in giving them a squirt or TWO. Thanks for the suggestions, Andy

19th Mar 2016, 12:56 pm	#10
Pitchfork Tetrode Join Date: Jan 2015 Location: Tadley, Hampshire, UK. Posts: 77	Re: Another Watkins Copicat problem http://wem-owners.com/links-contacts/contacts/

19th Mar 2016, 2:37 pm	#11
McMurdo Dekatron Join Date: Jun 2009 Location: Staffordshire Moorlands, UK. Posts: 5,271	Re: Another Watkins Copicat problem the last solid state copicat I had brought o me was the same; working when put away, not working when brought out. In this case it was pots so dirty they were open circuit. However I also had one with a short circuit electrolytic in there which had internally corroded in storage. __________________ Kevin

19th Mar 2016, 3:54 pm	#12
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: Another Watkins Copicat problem Can you get a wiring diagram (which may even have some voltages marked on it, if you're lucky) or at least partly reverse-engineer the circuit? Have you access to an oscilloscope? You really need to be able to follow an audio signal right through the circuit, and see where it is going missing. A piece of thin card or plastic should be enough to block the field from the erase head, by the way. __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.

20th Mar 2016, 12:57 pm	#13
Pitchfork Tetrode Join Date: Jan 2015 Location: Tadley, Hampshire, UK. Posts: 77	Re: Another Watkins Copicat problem I suggest that it need a service which will sort it out & have an earthed mains lead fitted at same time. I can do this for you rather than you trying to sort it yourself. Home made tape loops from old tape is not a good idea as if it is long-play it will be too thin. Refer to Wem owners link 2 posts ago for contact details

21st Mar 2016, 6:09 am	#14
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,662	Re: Another Watkins Copicat problem Schematics here http://www.vintagehofner.co.uk/brita...s/wemwire.html to find out which version you have see here http://www.vintagehofner.co.uk/brita...s/copicat.html Andy. __________________ Curiosity hasn't killed this cat...so far.

22nd Mar 2016, 2:42 pm	#15
boxdoctor Rest in Peace Join Date: Sep 2010 Location: Ripley, Derbyshire, UK. Posts: 785	Re: Another Watkins Copicat problem Failure of the bias oscillator was one of the main problems I experienced with this model. Usually just the two transistors going o\c. Yours suggests a problem in the record head amplifier circuit. I would, after ensuring that all pots and switches are really clean, replace all the small electrolytic caps, as these dry out, and after a long period of idleness may be completely open circuit. I've got one of these Mk4s myself, and it is reliable, presumably because it gets fairly regular use. Tony

9th May 2016, 5:50 pm	#16
The Sadows Retired Dormant Member Join Date: Mar 2016 Location: Isle of Wight, UK. Posts: 5	Re: Another Watkins Copicat problem Apologies for the long delay between posts. House refurbishment took priority. Thanks for all your suggestions. I do not have an oscilloscope so will have to rely on other forms of diagnostics, one being component substitution. Forgive my lack of electronic knowledge but are the record and playback heads the same? i.e. could I replace the record head with one of the playback heads? Thanks, Andy

13th May 2016, 5:33 pm	#17
Pitchfork Tetrode Join Date: Jan 2015 Location: Tadley, Hampshire, UK. Posts: 77	Re: Another Watkins Copicat problem The record & playback heads are the same but it may not be a head problem at all, but either an oscillator issue, a recording amp or the recovery circuit. Get it over to me to sort out I'm near Basingstoke - use a Courier it will cost <£8 to ship across, I fix these all of the time