Taylor 45C Valve Tester Data - UK Vintage Radio Repair and Restoration Discussion Forum

scope515 · 14th Apr 2007, 4:09 am

I want to test valve type 6CA7/EL34 but my data list for my 45C is not complete regarding this valve. Can anybody help me? Cheer, Neil

retailer · 14th Apr 2007, 11:43 am

Info I have is
Socket: 12
Base: IO1
Heater: 6.3v
Type: Pentode
Anode: 60
Screen: 60
Grid: 5
A: 4
B: 3
C: 0
GM: 5.0

igranic · 14th Apr 2007, 4:37 pm

Neil,

Care is needed with the ABC selector switches because: (i) there are several different versions of the 45c, (ii) errors in the valve charts are not unknown (see below), and (iii) you may get strange results if your Valve Chart is not the original supplied with the machine.

The manufacturer data sheets list the EL34 pin functions as follows:

1 = Suppressor Grid (g3)
2 = filament (F)
3 = Anode (a)
4 = Screen Grid (g2)
5 = Control Grid (g)
6 = either n/c or i/c
7 = Filament (F)
8 = Cathode (k)

But my 45c valve charts (I have two versions) give either:

4-3-0 which equates to:

1 C Cathode (k) (external connection to Suppressor Grid)
2 f Filament F2
3 A Anode
4 S Screen Grid (g²)
5 G Control Grid (g¹)
6 C Cathode (k)
7 F Filament F1 (cathode side)
8 C Cathode (k)

or

9-3-0 which equates to:

1 C Cathode (k) (external connection to Suppressor Grid)
2 f Filament F2
3 A Anode
5 G Control Grid (g¹)
4 S Screen Grid (g²)
6 C Cathode (k)
7 F Filament F1 (cathode side)
8 C Cathode (k)

The latter is clearly wrong since Screen Grid and Control Grid are reversed when compared to the data sheets. Probably a typographical error resulting from confusion between the numerals '4' and '9' when handwritten.

Enough of this waffle - let's cut to the chase!!!!
Since the manufacturer data sheets give pin 6 as either n/c (no connection) or i/c (internal connection), connecting pin 6 to the cathode circuit of the 45c could produce 'unexpected' results if the EL34 were internally connected to anything other than cathode or suppressor grid (g3). According to my working of the Valve Bases Wiring Chart, the more appropriate ABC setting would be 4-3-9, which leaves pin 6 open circuit.
i.e.

1 C Cathode (k)
2 f Filament F2
3 A Anode
4 S Screen Grid (g²)
5 G Control Grid (g¹)
6 - No Connection (n/c)
7 F Filament F1 (cathode side)
8 C Cathode (k)

You may like to look at this thread regarding the undocumented differences in the Taylor 45c. It would be very helpful if you could post a scan in that thread of the Valve Bases Wiring Chart (not circuit diagram) from your manual and/or valve chart.

HTH

scope515 · 15th Apr 2007, 8:43 am

I really appreciate the trouble you've gone to in your response, HTH. It sounds like it's not as simple as it should be. I'll look at my valve chart closely but take your advice with the ABC connections, ie 4-3-9 looks like the way to go.

I had a look at the other thread you suggested. It's all a minefield! I haven't a scanner so can't scan my wiring chart. However, it's not the same as any of them! Closest, though, to chart three.

Differences are:
Circuit 6: switch positions are same except for 11-A, 13-G, 16-C and 17-G.
Circuit 12 shown as 7 in mine plus slightly different switch positions, ie 11-C, 12-C, 13-C, 14-C and 16-S. No circuit 11 in mine chart. Serial number of my 45C is 295304, if that means anything. No date on manual. Cheers, Neil

retailer · 15th Apr 2007, 12:42 pm

I ran all of my EL34's ( a lone Telefunken, some RFT,Mullard and Philips Miniwatt, some Svetlana's and few Chinese ones) through my Taylor with no problems using the 430 setting.

What I have had problems with is Russian equivalent to EL84's, I can't recall the pin number but one of the NC/IC pins was connected to grid 1 causing the shorts test to return a positive result when in fact the valve was OK. Note that my other Russian EL84's which are Svetlana's, and labeled EL84 don't have this problem.

Back in 1967 a local electronics magazine ran a constructional article for a 60w guitar amp using 6DQ6's in the output. They chose to use an unused pin on the output valve socket to anchor the grid stopper resistor. All was fine as long as the original specified Miniwatt 6DQ6's were used, but try something like a Trigon 6DQ6 where that unused pin was connected internally to screen/g2 . The resulting +180v on the grid caused the anode to glow a nice cherry red less than 1/2 min after turn on and probably resulted on much head scratching until the penny dropped (me included).

The Taylor design engineers probably gave themselves a pat on the back for designing a tester that was not only quick to setup but also reduced the switch count by 6, but it does have its drawbacks.

scope515 · 15th Apr 2007, 2:50 pm

I've just finished doing the same, using both the 4-3-0 and 4-3-9 settings. Results all the same. I tested a range of different brands of NOS valves but am puzzled by the gm readings. The book says 5 yet all my NOS valves registered readings of around 3 to 4. Does this suggest the gm should be more like 3/3.5? Alternatively, could my tester be at fault in some way? Anode/screen/grid setting was 60/60/5. I'd be interested to know what you or others have found.

retailer · 17th Apr 2007, 12:52 pm

Mine seems to go the other way giving readings in the 6 - 6.5 region. I put this down to minor errors in the grid volts settings, hi slope valves like the el34 will accentuate small errors in the grid voltage setting.

14th Apr 2007, 4:09 am	#1
scope515 Retired Dormant Member Join Date: Feb 2005 Location: Perth Western Australia Posts: 6	Taylor 45C Valve Tester Data I want to test valve type 6CA7/EL34 but my data list for my 45C is not complete regarding this valve. Can anybody help me? Cheer, Neil

14th Apr 2007, 11:43 am	#2
retailer Heptode Join Date: May 2005 Location: Adelaide, South Australia Posts: 541	Re: Taylor 45C Valve Tester Data Info I have is Socket: 12 Base: IO1 Heater: 6.3v Type: Pentode Anode: 60 Screen: 60 Grid: 5 A: 4 B: 3 C: 0 GM: 5.0

14th Apr 2007, 4:37 pm	#3
igranic Rest in Peace Join Date: Jan 2005 Location: North Bedfordshire, UK. Posts: 395	Re: Taylor 45C Valve Tester Data Neil, Care is needed with the ABC selector switches because: (i) there are several different versions of the 45c, (ii) errors in the valve charts are not unknown (see below), and (iii) you may get strange results if your Valve Chart is not the original supplied with the machine. The manufacturer data sheets list the EL34 pin functions as follows: 1 = Suppressor Grid (g3) 2 = filament (F) 3 = Anode (a) 4 = Screen Grid (g2) 5 = Control Grid (g) 6 = either n/c or i/c 7 = Filament (F) 8 = Cathode (k) But my 45c valve charts (I have two versions) give either: 4-3-0 which equates to: 1 C Cathode (k) (external connection to Suppressor Grid) 2 f Filament F2 3 A Anode 4 S Screen Grid (g²) 5 G Control Grid (g¹) 6 C Cathode (k) 7 F Filament F1 (cathode side) 8 C Cathode (k) or 9-3-0 which equates to: 1 C Cathode (k) (external connection to Suppressor Grid) 2 f Filament F2 3 A Anode 5 G Control Grid (g¹) 4 S Screen Grid (g²) 6 C Cathode (k) 7 F Filament F1 (cathode side) 8 C Cathode (k) The latter is clearly wrong since Screen Grid and Control Grid are reversed when compared to the data sheets. Probably a typographical error resulting from confusion between the numerals '4' and '9' when handwritten. Enough of this waffle - let's cut to the chase!!!! Since the manufacturer data sheets give pin 6 as either n/c (no connection) or i/c (internal connection), connecting pin 6 to the cathode circuit of the 45c could produce 'unexpected' results if the EL34 were internally connected to anything other than cathode or suppressor grid (g3). According to my working of the Valve Bases Wiring Chart, the more appropriate ABC setting would be 4-3-9, which leaves pin 6 open circuit. i.e. 1 C Cathode (k) 2 f Filament F2 3 A Anode 4 S Screen Grid (g²) 5 G Control Grid (g¹) 6 - No Connection (n/c) 7 F Filament F1 (cathode side) 8 C Cathode (k) You may like to look at this thread regarding the undocumented differences in the Taylor 45c. It would be very helpful if you could post a scan in that thread of the Valve Bases Wiring Chart (not circuit diagram) from your manual and/or valve chart. HTH

15th Apr 2007, 8:43 am	#4
scope515 Retired Dormant Member Join Date: Feb 2005 Location: Perth Western Australia Posts: 6	Re: Taylor 45C Valve Tester Data I really appreciate the trouble you've gone to in your response, HTH. It sounds like it's not as simple as it should be. I'll look at my valve chart closely but take your advice with the ABC connections, ie 4-3-9 looks like the way to go. I had a look at the other thread you suggested. It's all a minefield! I haven't a scanner so can't scan my wiring chart. However, it's not the same as any of them! Closest, though, to chart three. Differences are: Circuit 6: switch positions are same except for 11-A, 13-G, 16-C and 17-G. Circuit 12 shown as 7 in mine plus slightly different switch positions, ie 11-C, 12-C, 13-C, 14-C and 16-S. No circuit 11 in mine chart. Serial number of my 45C is 295304, if that means anything. No date on manual. Cheers, Neil Last edited by Brian R Pateman; 16th Jan 2008 at 1:25 pm. Reason: Tidy up during archiving.

15th Apr 2007, 12:42 pm	#5
retailer Heptode Join Date: May 2005 Location: Adelaide, South Australia Posts: 541	Re: Taylor 45C Valve Tester Data I ran all of my EL34's ( a lone Telefunken, some RFT,Mullard and Philips Miniwatt, some Svetlana's and few Chinese ones) through my Taylor with no problems using the 430 setting. What I have had problems with is Russian equivalent to EL84's, I can't recall the pin number but one of the NC/IC pins was connected to grid 1 causing the shorts test to return a positive result when in fact the valve was OK. Note that my other Russian EL84's which are Svetlana's, and labeled EL84 don't have this problem. Back in 1967 a local electronics magazine ran a constructional article for a 60w guitar amp using 6DQ6's in the output. They chose to use an unused pin on the output valve socket to anchor the grid stopper resistor. All was fine as long as the original specified Miniwatt 6DQ6's were used, but try something like a Trigon 6DQ6 where that unused pin was connected internally to screen/g2 . The resulting +180v on the grid caused the anode to glow a nice cherry red less than 1/2 min after turn on and probably resulted on much head scratching until the penny dropped (me included). The Taylor design engineers probably gave themselves a pat on the back for designing a tester that was not only quick to setup but also reduced the switch count by 6, but it does have its drawbacks. Last edited by Brian R Pateman; 16th Jan 2008 at 1:28 pm. Reason: Tidy during archiving.

15th Apr 2007, 2:50 pm	#6
scope515 Retired Dormant Member Join Date: Feb 2005 Location: Perth Western Australia Posts: 6	Re: Taylor 45C Valve Tester Data I've just finished doing the same, using both the 4-3-0 and 4-3-9 settings. Results all the same. I tested a range of different brands of NOS valves but am puzzled by the gm readings. The book says 5 yet all my NOS valves registered readings of around 3 to 4. Does this suggest the gm should be more like 3/3.5? Alternatively, could my tester be at fault in some way? Anode/screen/grid setting was 60/60/5. I'd be interested to know what you or others have found.

17th Apr 2007, 12:52 pm	#7
retailer Heptode Join Date: May 2005 Location: Adelaide, South Australia Posts: 541	Re: Taylor 45C Valve Tester Data Mine seems to go the other way giving readings in the 6 - 6.5 region. I put this down to minor errors in the grid volts settings, hi slope valves like the el34 will accentuate small errors in the grid voltage setting.