Taylor Windsor 45B Valve Tester

[David Simpson]

My thanks to Martin(martiR2R) again for the Manual pdf.
Just opened up this old tester today for a shufti inside. As expected, C1 pretty cooked & gooey. Meter glass cracked & deposits of broken 6.3V bulb inside, but thankfully movement OK. Tested at 247.6uA
I cannot find the Rect.3 meter safety diodes, but guess a couple of b - b OA91's should do. I'm guessing Taylor buffs would recommend changing Rect.s 1 & 2. Any ideas ? Fingers crossed that the multi-tap T/F tests OK.
Cosmetically - a jolly good clean & a cabinet paint job is planned. Oh I, Taylor's valve data charts, are mentioned in the Manual. Are they readily available in pdf anywhere?

Regards, david

[karesz*]

Hallo David,
See at position #12 please, Grahams`s pdf....
Regards, karl

[David Simpson]

At last, this weekend, I've managed to find time to check back through 'Search' & see other guy's 45B experiences. johny17, karesz* & Uptown1 have provided a wealth of interesting gen. Hopefully, I'll get close to their successful endeavours.
I wonder if 250uA fsd is the common mc meter fitment in Taylor's range of 45's ?
My main concern is the state of the transformer. Everything else is hopefully fixable, now that the meter seems to be working ok.
I suppose that the question of Taylor v AVO v Mullard has arisen in the past, valve tester-wise. But, I have high hopes for this 45B. My only criticism of Taylors would be a lack of connection identification on that big paxolin tag board & on the transformer's tagboard. At least all the separate cable looms have coloured wiring. So circuit tracing shouldn't be too burdensome.

Regards, David

[johny17]

Hi I wish you good luck with the repair. Be careful with moving the solid wires because the are very prone to cut at the soldering points and then you will have to plan a visit to Delphi Oracle to find out where it was cut off . The cables from the transformers are flexible and not easily cut. After a respectable amount of hours spent at mine 45B it seems to me that the biggest issue would have been a hottish or blown transformer. All other problems can be repaired by an amateur (like me) with average electronics knowledge after a couple a hours or days or months of efforts.

[David Simpson]

Afaristo Yiannis, for your encouragement.
Delving into the innards of a Taylor is a new venture for me. I've checked a couple out in the past for friends, valve testing-wise, but thankfully they were ok. This old specimen is in need of a lot of tlc, but looks promising.
Now its springtime here, electronic work will have to compete with work outside on our smallholding. I bet Hellas & Kriti are awash with orange & lemon blossom in the countryside. I lived on Kypros for 3 years, over 40 years ago, but still miss the scents of the eastern Mediterranean. Not to mention the diving, & the wine.

Regards, David

[martiR2R]

Hi David, I have manuals for Taylor 45A, B, C, D and the 47A (and a very poorly 47A itself), they all appear to use a 250ua meter. I also have the valve charts if you need them.
Regards
Martin

[David Simpson]

Thanks Martin. I've had the 45A & 45C Manuals since I played with other Taylors some years back. But I wasn't sure if all the 45 series used the same meter movement. Am I glad that this one is working fine, but I'll need to source a glass. I guess Taylor meters, like AVO's, are getting as rare as rocking horse manure. And expensive, no doubt.
Talking of AVO VCM's, it would be great if some software whizz kid could adapt the AVO VD Manual's thumbwheel codes to Taylor's switch setting data charts. Wonder if anyone has tried it ?
Graham(aka StationX) has kindly sent me the pdf data charts. So next grotty weather day I'll carry on with this 45B. My initial thoughts are that, like AVO, Taylor test their amplifier valves at the lower end of the gm graph. No doubt avoidance of parasitic oscillation is a priority. No evidence of ferrite beads, I see. I'll leave testing one of my VT136's till the very end of the project. They are a fearsome high slope valve with a strong propensity to PO.

Regards, David

[David Simpson]

Think I'm going doolally - Just passing my workshop door on my way out & suddenly thought - the circuit diagram in the 45B manual copy which Martin sent me has two mains transformers(as does the parts list = T1 & T2) ! But hey, this 45B of mine just has one, and the circuit diagrams in the 45A & 45C Manual copies I have - just have one !
If Taylor modified their 45B's back on 4/4/51(date on c/d) to two transformers, why didn't 45C's have two T/F's, being the later upgraded version ?

Regards, David

[martiR2R]

This doesn't help but the info I have =

45A/47A - cct dia. shows 1 Tx - Parts list - don't have one
45B - cct dia shows 2 Tx - Parts list - shows T1 + T2
45C - cct dia shows 1 Tx - Parts list - shows T1 + T2
45D - cct dia shows 2 Tx - Parts list - shows T1 + T2


Martin

[David Simpson]

Folks, I've finished the EMI WM1 scope, and can now return to this curious 1 transformer version of a 45B.
Two tag boards predominate the circuitry. One on top of the T/F & one behind the Meter. I wonder why Taylor didn't follow AVO & Mullard and provide component diagrams &/or tag board connection lists. Have any Taylor experts out there done any, I wonder ? If not, I'll have a go myself, but suspect that it would take some time, as the interconnection wiring seems to have a random choice of colours.
First - a thorough test of the T/F. I'd done some quick voltage checks back in May, & they seemed OK. Now - where is that big Megger SL2, insulation tests are next.

Regards, David

[David Simpson]

Further thoughts:-
I think I mooted the idea of a cabinet change for this 45B in my thread about a J-J Phasor Meter, a few weeks back. Am giving it more thought. A low profile desk format certainly looks good compared to the old 1950's rusty cabinet. Ergonomically, (is that the correct term ?), it looks easier & safer to use, and there is extra space for additional Va, Ia, & Vg metering & fusing.

Regards, David

[David Simpson]

Folks, why would R3(100K) & R9((27K) be wired directly in series(on the back of SW3's 4R) without any connections from the join to 3R & 3F connections 5( Cathode Leakage),(which are shown on the circuit diagram)?
These two wee 1/8W resistors were hidden inside a wee ancient brown lacquered cloth sleeve, and the soldered connections on the wafer switch were well covered with red loctite(as were all other soldered connections). Not a recent bodge job, more like an original factory installation from the 50's.

Regards, David

[David Simpson]

I've drawn up connection diagrams for the Heater SW1, the single transformer's Tag Board, and the main component tag board. They might be of use to other single transformer 45B owners, but I would like to hear if other 45B's have the same wiring colour coding & tag connections ? I've cut the loom to the Valve Holder Panel & fitted a new term strip to the main component tag board which sits on the back of the meter.
Wisdom dictates changing the old selenium rectifiers & fitting safety diodes to the meter. Any recommendations for modern silicon fitments ?
The more I've delved into the 45B's innards & perused the circuit diagram - the more I'm thinking that these valve testers could give the AVO 2 Panel, and Mk's 1 & 2 a run for their money. Just a pity that the casing is a bit tinny.
What appears to be factory fitted resistors - differ somewhat in colour coded values from those given on the circuit diagram's list. The right hand side of that list refers to a number of Taylor Drawing Numbers. Obviously its just the 15 page User's Instructional Manual that floats amongst the vintage fraternity. But, there must have been a 2nd or 3rd line repair or manufacturers Manual back in the 50's & 60's. Who's got one ?

Regards, David

[David Simpson]

More progress. Like the AVO VCM's, the 45B puts full AC sinewave on the anode, and a half-wave negative going pulse on the grid. 100V Va selected gives 300 P-P on the Anode, and 10V Vg selected gives a 30V peak pulse on the Grid which the DMM reads as -4V DC.
Trying to get mA/V readings was rather hit & miss - due to Pots A & B being hellish sticky. So stripped all three 2K pots & gave them a good clean. Hey - nothing in the Manual about R13 - the 'A' pot - being a three segment winding, similar to a CT160's RV2. In fact, cant remember anyone else mentioning it, unless I've missed a post somewhere. First 90 deg segment is 0 - 25 ohms, 2nd is 25 - 150 ohms, and the 3rd is 150 - 2000 ohms, turning clockwise.
Folk might remember me banging on, a while back, about higgledy-piggledy wiring by post-war Marconi employees. Well, the person who wired this 45B is Mr H - P himself. The worst I've ever seen. Not to mention the awful wrapping of wires through & round tags & terminations! IO8/1 valve holder was knackered, so needed replacing. No matter how I tried - the only way to disconnect the wiring was to snip off the valve holder's underside tags, and re-solder them to a new valve holder's tags. Yep - could've replaced some of the underside wiring, but Jesus - the inter-valve holder wiring was twisted left & right , & up & down. Completely random, direction-wise.
Frustrating perseverance is the method needed for 45B repairs , I submit.

Regards, David

[David Simpson]

Calling all Taylor 45 series valve tester owners/ restorers - - Is a 3 segment 1 3/4", wire-wound enclosed 2K ohm pot in common use for all the 'A' Pot fitments ? If so - why ?
If AVO NOS prices are anything to go by for the RV2 10K three segment Pot, then they are as rare as rocking horse manure.

Regards, David

[Freya]

Hi David,

As a Taylor collector, I have been reading and keeping up with all your posts which are very interesting.
The Taylor 45B was the first to use the triple segment special pot, they seem to be quite easily worn out with the repetition, which manifests in bunching of the resistance on the former or hairy ends showing.
There seems to be no particular serial number when Taylor switched the special 2k on the 45C, I have seen combinations of carbon, wire wound and the special fitted, the most up to date idea is the multi turn pots that are now available quite cheaply.
Out of all of them the special is the most accurate when testing output pentodes when the needle fly's over at the slightest touch of the A control.

[David Simpson]

Thanks Stephen for your reply. I wonder who brought in the 3 segment pot first ? Taylor or AVO ? AVO took over Taylor in 1957, and introduced the CT160 along with it's 10K RV2 about the same time.
Right enough, fsd needle whanging could be a problem with o/p valves. With this 45B I started gently with a 6J5GT, then a Pen36C, then an EL33, then a KT63. All valves first tested on my AVO Mk3. Initial results promising with mA/V readings within 5 to 10% of the AVO's. But a slight tweak of the Taylor's grid pot could bring the meter spot-on. A wee bit of calibration will be needed I suspect.
This 45B's s/no is 250030 by the way. I wonder if this could place it chronologically.

Regards, David

[Freya]

I have always thought that a more accurate display of the grid volts would be a good idea, I had ideas of bringing out a separate box with a few meters fitted to show the various voltages etc, the tester would remain totally functional regardless if it was plugged in or not.

[David Simpson]

Trouble is, Stephen- Like AVO VCM's, the Taylor's RMS values of Va, Vs, Vg are of little value for calibration purposes. Right enough, there is a measurable DC component for Vg, and to a lesser extent Va. However, valves only conduct every 20mS, and even then only for a possible duration of 5 or 6 mS when the peaking values are nearish to a valve's working voltages. Measurable(using 1950's M-meters) RMS values of Ia & Vg will never be more than half of expected valve data book values. Also, AC valve testers usually work at the lower region of the Ia/Vg ch. curve, and don't use high values of delta Vg to obtain mA/V. The Taylor seems to do this by shorting out either of the two cathode bias resistors. A decent -ve Vg from R15 obviously holds the valve back from drawing excessive Ia when either R6 or R7 is shorted by the Meter push button sw.
Anyway, I'm impressed with the Taylor 45B

Regards, David