Ferguson 393G Record Player - Curious fault - UK Vintage Radio Repair and Restoration Discussion Forum

awc · 11th Jul 2017, 10:21 am

This has been a frustrating repair in a way I expect many of you have experienced yourself, insofar as the restored player worked perfectly on the bench, but started to play up when back in the box.

This player uses two UCL83's in push-pull and the heaters are run in series with the dial bulb and a low voltage motor on the Collaro Challenger deck.

What happened is that after working fine to start with, the sound became occasionally intermittent. I have substituted the cartridge, the cartridge pins, the two valves, tried adjusting the tracking etc all to no avail.

Running a CD player as input also caused the fault to appear.

Curiously, the fault seems to disappear at higher volumes and stranger still, at lower volumes with no signal input, the amp cuts out altogether, to instantly come alive again if the input terminal is touched with a screwdriver. It tends to fade away slowly though with no signal input after between 10 and 50 secs on average.

Repairs included new valves, all caps (except the smoothing-reservoir) the rectifier replaced with a 1N4007 /resistor as usual and the signal lead which had gone stiff and was restricting arm movement.

Any thoughts anyone before I try changing all the resistors as well!

Thanks

Alex

Station X · 11th Jul 2017, 10:28 am

Have you tried checking voltages when the fault is present? If they're correct it'll enable you to eliminate parts of the circuit as the cause of the problem.

Boater Sam · 11th Jul 2017, 10:34 am

Sounds like a dry soldered joint - probably.
Leave you meter on the anodes of the pentodes and see what happens to the voltage as the fault appears.
If nothing, try the same on the screen grids of the pentodes. If nothing again, try the triode anodes. This should point you in the right direction.

Refugee · 11th Jul 2017, 10:34 am

That sounds like a classic case of shorting of a signal wire when fitting the covers.
As long as you are not getting red plating it will most likely be one of the triode sections being driven hard on or off killing the signal.
Look out for coupling capacitors that are standing proud of the chassis when it is out of the cabinet.

Edward Huggins · 11th Jul 2017, 4:01 pm

Also - be careful to check the condition of the large value capacitor in the feedback loop. This helps determine the bass response, which is excellent on this player. Do note the 6.5" speaker has a twin cone (rare on a portable) and this allows for a sweet treble.

peter_sol · 11th Jul 2017, 5:49 pm

It could be the loudspeaker at fault.

Telegraph-Hill · 11th Jul 2017, 6:40 pm

Had this problems quite often, yes try to connect a different loudspeaker also. Maybe check the output transformer for the speaker especially the connections to the thin wires going to the coils.

Cheers, Oliver

awc · 11th Jul 2017, 10:17 pm

Ah. Here I have to declare that I have replaced the speaker as the original had completely seized up due to rust and is irreparable. The replacement is a more modern 4 ohm 10 watt unit with a silver centre dome and (when the player is performing correctly) sounds great. I didn't mention it as I couldn't see what possible bearing it could have on a fault which appears on the face of it to originate on the input.

Anyway I have taken all the advice on board and will check out the various ideas.

Alex

awc · 13th Jul 2017, 5:18 pm

Well it would seem the problem has been solved and the player is now working nicely.

What was it caused the grief I hear you cry!

I must confess to being responsible for fault No.1, as I discovered on close (very close!) inspection of the cartridge pins that the problem was down to poor soldering on my part. I would explain that the signal wires have been replaced using the earphone cable from a £1 pair of earphones. This is very thin and flexible and works very well without introducing any hum. In the cable there are two fine wires , one is enamelled and the other bare. Although I had scraped off the enamel from the end of the wire, when soldering it to the pin I had succeeded in only soldering the enamelled part leaving the bared end sticking out. What was happening when I was touching the terminal with a screwdriver was that I was briefly making contact. Dohhh

Fault No.2 did transpire to be in the speaker area, though not the speaker itself. Someone in the past had inserted a 1/4in jack changeover socket in the wire from the amp to the speaker to enable an external speaker to be used. I hadn't given this any thought. I decided to use it to connect up my test speaker, which appeared to work fine. When removing it however, the main speaker became crackly and on close examination of the socket I found the contacts were distorted and badly tarnished. Removing it altogether has restored normal operation.

Lessons to be learned eh.

Many thanks to all responders for your help once again

Alex

Edward Huggins · 13th Jul 2017, 5:46 pm

I'm glad you are back using the orginal speaker, this is a nice unit and will give an extended treble. When working on the amplifier be careful not to stress the PC Board as at 60 years old it can become very brittle. If there is too much bass on some tracks, just lift up the roller top a bit to create about a 1" gap.

11th Jul 2017, 10:21 am	#1
awc Retired Dormant Member Join Date: Jul 2005 Location: Somerset, UK. Posts: 334	Ferguson 393G Record Player - Curious fault This has been a frustrating repair in a way I expect many of you have experienced yourself, insofar as the restored player worked perfectly on the bench, but started to play up when back in the box. This player uses two UCL83's in push-pull and the heaters are run in series with the dial bulb and a low voltage motor on the Collaro Challenger deck. What happened is that after working fine to start with, the sound became occasionally intermittent. I have substituted the cartridge, the cartridge pins, the two valves, tried adjusting the tracking etc all to no avail. Running a CD player as input also caused the fault to appear. Curiously, the fault seems to disappear at higher volumes and stranger still, at lower volumes with no signal input, the amp cuts out altogether, to instantly come alive again if the input terminal is touched with a screwdriver. It tends to fade away slowly though with no signal input after between 10 and 50 secs on average. Repairs included new valves, all caps (except the smoothing-reservoir) the rectifier replaced with a 1N4007 /resistor as usual and the signal lead which had gone stiff and was restricting arm movement. Any thoughts anyone before I try changing all the resistors as well! Thanks Alex

11th Jul 2017, 10:28 am	#2
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Ferguson 393G Record Player - Curious fault Have you tried checking voltages when the fault is present? If they're correct it'll enable you to eliminate parts of the circuit as the cause of the problem. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

11th Jul 2017, 10:34 am	#3
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Ferguson 393G Record Player - Curious fault Sounds like a dry soldered joint - probably. Leave you meter on the anodes of the pentodes and see what happens to the voltage as the fault appears. If nothing, try the same on the screen grids of the pentodes. If nothing again, try the triode anodes. This should point you in the right direction.

11th Jul 2017, 10:34 am	#4
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,554	Re: Ferguson 393G Record Player - Curious fault That sounds like a classic case of shorting of a signal wire when fitting the covers. As long as you are not getting red plating it will most likely be one of the triode sections being driven hard on or off killing the signal. Look out for coupling capacitors that are standing proud of the chassis when it is out of the cabinet.

11th Jul 2017, 4:01 pm	#5
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,335	Re: Ferguson 393G Record Player - Curious fault Also - be careful to check the condition of the large value capacitor in the feedback loop. This helps determine the bass response, which is excellent on this player. Do note the 6.5" speaker has a twin cone (rare on a portable) and this allows for a sweet treble. __________________ Edward.

11th Jul 2017, 5:49 pm	#6
peter_sol Octode Join Date: Aug 2003 Location: Welwyn Garden City, Herts. UK. Posts: 1,906	Re: Ferguson 393G Record Player - Curious fault It could be the loudspeaker at fault.

11th Jul 2017, 6:40 pm	#7
Telegraph-Hill Triode Join Date: Mar 2017 Location: Totnes, Devon, UK. Posts: 27	Re: Ferguson 393G Record Player - Curious fault Had this problems quite often, yes try to connect a different loudspeaker also. Maybe check the output transformer for the speaker especially the connections to the thin wires going to the coils. Cheers, Oliver

11th Jul 2017, 10:17 pm	#8
awc Retired Dormant Member Join Date: Jul 2005 Location: Somerset, UK. Posts: 334	Re: Ferguson 393G Record Player - Curious fault Ah. Here I have to declare that I have replaced the speaker as the original had completely seized up due to rust and is irreparable. The replacement is a more modern 4 ohm 10 watt unit with a silver centre dome and (when the player is performing correctly) sounds great. I didn't mention it as I couldn't see what possible bearing it could have on a fault which appears on the face of it to originate on the input. Anyway I have taken all the advice on board and will check out the various ideas. Alex

13th Jul 2017, 5:18 pm	#9
awc Retired Dormant Member Join Date: Jul 2005 Location: Somerset, UK. Posts: 334	Re: Ferguson 393G Record Player - Curious fault Well it would seem the problem has been solved and the player is now working nicely. What was it caused the grief I hear you cry! I must confess to being responsible for fault No.1, as I discovered on close (very close!) inspection of the cartridge pins that the problem was down to poor soldering on my part. I would explain that the signal wires have been replaced using the earphone cable from a £1 pair of earphones. This is very thin and flexible and works very well without introducing any hum. In the cable there are two fine wires , one is enamelled and the other bare. Although I had scraped off the enamel from the end of the wire, when soldering it to the pin I had succeeded in only soldering the enamelled part leaving the bared end sticking out. What was happening when I was touching the terminal with a screwdriver was that I was briefly making contact. Dohhh Fault No.2 did transpire to be in the speaker area, though not the speaker itself. Someone in the past had inserted a 1/4in jack changeover socket in the wire from the amp to the speaker to enable an external speaker to be used. I hadn't given this any thought. I decided to use it to connect up my test speaker, which appeared to work fine. When removing it however, the main speaker became crackly and on close examination of the socket I found the contacts were distorted and badly tarnished. Removing it altogether has restored normal operation. Lessons to be learned eh. Many thanks to all responders for your help once again Alex

13th Jul 2017, 5:46 pm	#10
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,335	Re: Ferguson 393G Record Player - Curious fault I'm glad you are back using the orginal speaker, this is a nice unit and will give an extended treble. When working on the amplifier be careful not to stress the PC Board as at 60 years old it can become very brittle. If there is too much bass on some tracks, just lift up the roller top a bit to create about a 1" gap. __________________ Edward.