Taylor 45C repair issue - UK Vintage Radio Repair and Restoration Discussion Forum

rcaradiola · 20th Apr 2014, 1:35 am

Greetings! I am currently working on a Taylor 45C valve tester. I have replaced C1 (.1uF, 300V) and all of the out of spec resistors. When I got to SW3 (Main Selector Switch) I discovered something unusual: There is a 120K resistor (R3?) on the 4R wafer section of the switch. In series with R3 there is a 75K resistor, also connected to the 4R wafer section. This resistor is not listed on the component list. The point where the 75K resistor is soldered on 4R still has the factory pinkish-red paint present. This point is jumpered to the point on the 3R wafer. The solder point is directly below the 4R point.

When testing a valve with the Main Selector Switch in the Fil. Cont. position the meter pegs hard right.

I later discovered that the 2K ohm Grid potentiometer (R15) has experienced an over current episode. The high side of the strip that the wire is wound on is burned (approximately 3cm worth).

I'm not sure where to go from here to solve this problem with this valve tester.

Regards,
Donald

Freya · 21st Apr 2014, 8:01 pm

can you post some internal pictures, there are a few versions of the 45c as it evolved. I may be able to match it with one of mine.

rcaradiola · 22nd Apr 2014, 2:21 pm

Stephen: Hi and good afternoon! Find attached 3 docs with the pictures you requested. My jpg's were too large so I put them on the .doc format. In pg. 2 I added the 220 ohm resistor seen on the (+) terminal of the meter.

Regards,
Donald

Freya · 22nd Apr 2014, 2:59 pm

Hi Donald,

Not popped the lids on mine yet but already I can see from the pictures that yours is the final variation out of the factory.
What's the serial number?

rcaradiola · 22nd Apr 2014, 11:28 pm

Stephen: Hi! It is T295241.

Regards,
Donald

rcaradiola · 25th Apr 2014, 10:15 pm

Stephen: Hi again! Can a bad diode cause these problems?

Regards,
Donald

Freya · 25th Apr 2014, 10:33 pm

Donald,

I have two testers that have had their rectifiers replaced with GEX34 diodes, my only thought is that the originals failed in some way. I see from your pictures that some soldering has been done maybe to the resistors above the transformer, also a wire wound resistor has been replaced on the PCB.

It is possible that a bad valve has done some damage previously, and not all the affected parts have been found.
Your tester is a very late model.

kenneth · 26th Apr 2014, 4:44 pm

Hi Donald, Don't think I can help your much . My 45c is serial no. T430452.
My understanding is that the two resistors connected together to the rear of wafer 4 are R3 (127k) and R18 (75k). The point where they are soldered together appears to be only used as a convenient solder tag. R18 is not shown on the component list that I have but it is shown on my circuit diagram.
I have been unable to locate an R9 in my tester and it is not shown on my circuit diagram although it is included on the list of components that I have. I do, though, have part of a circuit diagram (downloaded from this forum) that shows R9. Judging by your pics it looks like you (or someone) has added R9 to your tester - if so I would be interested to know what difference (if any) it made.

Regards Ken.

rcaradiola · 27th Apr 2014, 12:10 am

Greetings! Does anybody have the test parameters for the RECT. 1 and RECT. 2? Will 1N4007 diodes work as a replacement?

Best regards,
Donald

20th Apr 2014, 1:35 am	#1
rcaradiola Retired Dormant Member Join Date: Sep 2013 Location: Beaverhead County, Montana, USA. Posts: 22	Taylor 45C repair issue Greetings! I am currently working on a Taylor 45C valve tester. I have replaced C1 (.1uF, 300V) and all of the out of spec resistors. When I got to SW3 (Main Selector Switch) I discovered something unusual: There is a 120K resistor (R3?) on the 4R wafer section of the switch. In series with R3 there is a 75K resistor, also connected to the 4R wafer section. This resistor is not listed on the component list. The point where the 75K resistor is soldered on 4R still has the factory pinkish-red paint present. This point is jumpered to the point on the 3R wafer. The solder point is directly below the 4R point. When testing a valve with the Main Selector Switch in the Fil. Cont. position the meter pegs hard right. I later discovered that the 2K ohm Grid potentiometer (R15) has experienced an over current episode. The high side of the strip that the wire is wound on is burned (approximately 3cm worth). I'm not sure where to go from here to solve this problem with this valve tester. Regards, Donald

21st Apr 2014, 8:01 pm	#2
Freya Octode Join Date: Jan 2009 Location: Falmouth, Cornwall, UK. Posts: 1,991	Re: Taylor 45C repair issue can you post some internal pictures, there are a few versions of the 45c as it evolved. I may be able to match it with one of mine. __________________ Stephen _________"It`s only an old telly" ___

22nd Apr 2014, 2:59 pm	#4
Freya Octode Join Date: Jan 2009 Location: Falmouth, Cornwall, UK. Posts: 1,991	Re: Taylor 45C repair issue Hi Donald, Not popped the lids on mine yet but already I can see from the pictures that yours is the final variation out of the factory. What's the serial number? __________________ Stephen _________"It`s only an old telly" ___

22nd Apr 2014, 11:28 pm	#5
rcaradiola Retired Dormant Member Join Date: Sep 2013 Location: Beaverhead County, Montana, USA. Posts: 22	Re: Taylor 45C repair issue Stephen: Hi! It is T295241. Regards, Donald

25th Apr 2014, 10:15 pm	#6
rcaradiola Retired Dormant Member Join Date: Sep 2013 Location: Beaverhead County, Montana, USA. Posts: 22	Re: Taylor 45C repair issue Stephen: Hi again! Can a bad diode cause these problems? Regards, Donald

25th Apr 2014, 10:33 pm	#7
Freya Octode Join Date: Jan 2009 Location: Falmouth, Cornwall, UK. Posts: 1,991	Re: Taylor 45C repair issue Donald, I have two testers that have had their rectifiers replaced with GEX34 diodes, my only thought is that the originals failed in some way. I see from your pictures that some soldering has been done maybe to the resistors above the transformer, also a wire wound resistor has been replaced on the PCB. It is possible that a bad valve has done some damage previously, and not all the affected parts have been found. Your tester is a very late model. __________________ Stephen _________"It`s only an old telly" ___

26th Apr 2014, 4:44 pm	#8
kenneth Retired Dormant Member Join Date: Apr 2005 Location: Cheltenham, Gloucestershire, UK. Posts: 173	Re: Taylor 45C repair issue Hi Donald, Don't think I can help your much . My 45c is serial no. T430452. My understanding is that the two resistors connected together to the rear of wafer 4 are R3 (127k) and R18 (75k). The point where they are soldered together appears to be only used as a convenient solder tag. R18 is not shown on the component list that I have but it is shown on my circuit diagram. I have been unable to locate an R9 in my tester and it is not shown on my circuit diagram although it is included on the list of components that I have. I do, though, have part of a circuit diagram (downloaded from this forum) that shows R9. Judging by your pics it looks like you (or someone) has added R9 to your tester - if so I would be interested to know what difference (if any) it made. Regards Ken. Last edited by kenneth; 26th Apr 2014 at 4:52 pm. Reason: punctuation

27th Apr 2014, 12:10 am	#9
rcaradiola Retired Dormant Member Join Date: Sep 2013 Location: Beaverhead County, Montana, USA. Posts: 22	Re: Taylor 45C repair issue Greetings! Does anybody have the test parameters for the RECT. 1 and RECT. 2? Will 1N4007 diodes work as a replacement? Best regards, Donald