Taylor 45D Calibration and Tech Details - UK Vintage Radio Repair and Restoration Discussion Forum

Matthew kane · 17th Jan 2021, 7:38 am

So the restoration itch has kicked in again after 8 years I finally have a 45D coming my way this week.

Is there any specific tech service details or manuals for this tester covering calibration points and key parts to measure/replace if needed fundamental to the operation of the tester? Also what is the FSD resistance/mV per ohm and current measurement of the meter and scale deflection angle if known?

Thanks

factory · 17th Jan 2021, 11:41 am

Someone asked about the meters in the 45B & 45C recently, the 45A, 45B, 45C & 45D all have a meter with a 250uA F.S.D. if that helps (45 with no letter is different).

Here are the instructions, which include a parts list, which I think I found on the forum.
45D_operating.pdf

I can't help much more as I never bought one in the end and they are now too expensive to consider.

David

Matthew kane · 23rd Jan 2021, 4:48 am

Thanks for that, looks like my unit went through a service centre here sometime ago as there was a very old looking printed manual stapled into a booklet with some notes in the back schematics section.

Having a quick look inside the board behind the meter, there seems to be a slider based trimmer resistor to I’d assume adjust the resistance the circuit should see from meter similar to how the ‘swamp’ resistor works in the early AVO testers.

The manual also notes there was a later iteration of the 45D called the D2 which had a 3 x multiplier to measure 3 times the transconductance compared to the 2 x multiplier of the normal 45D tester.

Overall very simple circuit and very clean inside my unit. Have started refinishing the panels and disposed of the old AC cable.

Can the two black box styled diodes/half wave rectifiers be replaced with a 1kv/1A modern part, a’la 1N4007 or similar?

factory · 23rd Jan 2021, 1:40 pm

There are many threads about the 45D & 45D2, I would suggest a search through the old threads for common problems with these.

If you find any black Hunts capacitors then they should be replaced as they are wax paper types.

The rectifiers, you will need to work out a series resistor value to get the correct voltage from the grid control, as the metal rectifiers have a much larger voltage drop compared with modern diodes.

If you didn't get a valve chart with it, the AVO ones can apparently be used for these.

David

Matthew kane · 25th Jan 2021, 8:29 am

Thanks I got an original valve book so all good. Did some modification by hooking up a trafo that can go up to 1.25kv at 250mA and a separate meter and tested some NOS Taylor 572B and got pretty close to gm rating originally tested from manufacturer. Going to 3d print some teflon parts as replacement.

17th Jan 2021, 7:38 am	#1
Matthew kane Tetrode Join Date: May 2019 Location: Melbourne, Victoria, Australia. Posts: 66	Taylor 45D Calibration and Tech Details So the restoration itch has kicked in again after 8 years I finally have a 45D coming my way this week. Is there any specific tech service details or manuals for this tester covering calibration points and key parts to measure/replace if needed fundamental to the operation of the tester? Also what is the FSD resistance/mV per ohm and current measurement of the meter and scale deflection angle if known? Thanks

17th Jan 2021, 11:41 am	#2
factory Octode Join Date: Jul 2009 Location: Cheshire, UK. Posts: 1,732	Re: Taylor 45D Calibration and Tech Details Someone asked about the meters in the 45B & 45C recently, the 45A, 45B, 45C & 45D all have a meter with a 250uA F.S.D. if that helps (45 with no letter is different). Here are the instructions, which include a parts list, which I think I found on the forum. 45D_operating.pdf I can't help much more as I never bought one in the end and they are now too expensive to consider. David Last edited by factory; 17th Jan 2021 at 11:46 am.

23rd Jan 2021, 4:48 am	#3
Matthew kane Tetrode Join Date: May 2019 Location: Melbourne, Victoria, Australia. Posts: 66	Re: Taylor 45D Calibration and Tech Details Thanks for that, looks like my unit went through a service centre here sometime ago as there was a very old looking printed manual stapled into a booklet with some notes in the back schematics section. Having a quick look inside the board behind the meter, there seems to be a slider based trimmer resistor to I’d assume adjust the resistance the circuit should see from meter similar to how the ‘swamp’ resistor works in the early AVO testers. The manual also notes there was a later iteration of the 45D called the D2 which had a 3 x multiplier to measure 3 times the transconductance compared to the 2 x multiplier of the normal 45D tester. Overall very simple circuit and very clean inside my unit. Have started refinishing the panels and disposed of the old AC cable. Can the two black box styled diodes/half wave rectifiers be replaced with a 1kv/1A modern part, a’la 1N4007 or similar?

23rd Jan 2021, 1:40 pm	#4
factory Octode Join Date: Jul 2009 Location: Cheshire, UK. Posts: 1,732	Re: Taylor 45D Calibration and Tech Details There are many threads about the 45D & 45D2, I would suggest a search through the old threads for common problems with these. If you find any black Hunts capacitors then they should be replaced as they are wax paper types. The rectifiers, you will need to work out a series resistor value to get the correct voltage from the grid control, as the metal rectifiers have a much larger voltage drop compared with modern diodes. If you didn't get a valve chart with it, the AVO ones can apparently be used for these. David

25th Jan 2021, 8:29 am	#5
Matthew kane Tetrode Join Date: May 2019 Location: Melbourne, Victoria, Australia. Posts: 66	Re: Taylor 45D Calibration and Tech Details Thanks I got an original valve book so all good. Did some modification by hooking up a trafo that can go up to 1.25kv at 250mA and a separate meter and tested some NOS Taylor 572B and got pretty close to gm rating originally tested from manufacturer. Going to 3d print some teflon parts as replacement.