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Old 23rd Mar 2010, 11:07 pm   #261
swordholder
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Default Re: The "Sussex" Homebrew Valve Tester.

Rob,
The transformer runs cool in my tester which isn't ventilated
Mike
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Old 24th Mar 2010, 6:34 pm   #262
Guitarist28
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Default Re: The "Sussex" Homebrew Valve Tester.

I have created an xray version of the main circuit board (attached) to help with position of the components whilst populating the board. Please note that it is from an earlier version as this was the best overlay that I could manage using Photoshop (my skills aren't that high to do any better with this software) so it needs to be used in conjunction with Top Caps schematic/board connections.

I'm happy to provide a larger copy or the Photoshop files if anyone else wants to have a go and improve this please PM me.

I hope this may be helpful.

Regards

Rob

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Old 24th Mar 2010, 7:44 pm   #263
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi Gents, the transformer is designed to run cool (max hand heat 45C) when on the correct mains tapping and not being used to soak test a power pen for an extended time.

Ed
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Old 24th Mar 2010, 7:57 pm   #264
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi Ed,
Thanks for the info which will aide the final case design.

Regards

Rob
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Old 24th Mar 2010, 8:54 pm   #265
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Default Re: The "Sussex" Homebrew Valve Tester.

I hope to include a diode setting in my Sussex and I would like to use the AVO book for reference.
Looking at the AVO Mk IV diagram the ranges appear to be.
1mA @ 60V
5mA @ 60V|
15mA @ 60V
30mA @ 60V
60mA @ 100V
120mA @ 175V
180mA @ 225V

The 120mA and 180mA ranges will be for short duration intermittent use only.

I have posted a diagram below it is in 2 parts as the program that I used to create it only allows a certain number of components on each sheet. There are no interconnections between the two parts which should make it easier to follow.

The existing function switch will be changed for a 5 pole 11 throw (marked as S1 in the diagram) and the A1, A2 switch will be replaced with a 3 pole 4 throw one (marked as S2 in the diagram)
The existing wiring is wired into the first 4 positions of S1a, S1b, S1c

S2b selects A1,A2 and S2c selects D1,D2 and RLA switches between them. This arrangement prevents a diode been accidentally connected when the function switch is not at a diode setting.
S2a enables A1, A2, D1 or D2 to be selected while the function switch is set to ANODE S/C or GRID2 S/C.

S1d sets the appropriate voltage for TR2 base while in diode test mode.
S1e sets the appropriate limit

R6 will be change for a value that gives a 1mA current limit, R7 will be removed and the wires from S1e connected in its place. Values for the resistors around S1e has not been determined yet as I suspect that some experimentation may be needed.

This all theory yet so there may be errors in it.
Dose it sound feasible?

The 5 pole 11 throw BBM switch are available from Kwtubes shop in ebay in lots of 4. (I have no connection with them) it is advertised as a 10 throw switch but if the stop washer is removed or the stop pin is broken off the stop washer the 11th position can be used.

Frank
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File Type: pdf REC_TESTER_SWITCH_PT2.pdf (10.7 KB, 496 views)
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Old 27th Mar 2010, 11:57 am   #266
Guitarist28
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi Swordholder,
I am currently working on the gas test part of the circuit and you have indicated a coil between Junc27/C11 and the gas test button yet the coil is not included in the BOM. Have I missed something here and what type of coil do you recommend.

Regards

Rob
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Old 27th Mar 2010, 12:25 pm   #267
Andymic
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Default Re: The "Sussex" Homebrew Valve Tester.

Rob,

Where does he mention a coil?

Andy
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Old 27th Mar 2010, 12:34 pm   #268
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi Andy,
Have a look at page 7 of this thread about halfway down where Mike describes the mod with 2 attachments.

Regards

Rob
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Old 27th Mar 2010, 12:46 pm   #269
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Default Re: The "Sussex" Homebrew Valve Tester.

Rob,

I think that's the coil of the relay............

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Old 27th Mar 2010, 12:52 pm   #270
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Default Re: The "Sussex" Homebrew Valve Tester.

Andy,
Thanks

Rob (or possibly Homer Simpson! Doh!!)
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Old 27th Mar 2010, 6:22 pm   #271
Sean Williams
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Default Re: The "Sussex" Homebrew Valve Tester.

If anyone wants access to a guillotine and small sheet metal folder, they only have to ask....

Cheers
Sean
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Old 27th Mar 2010, 8:45 pm   #272
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi All,
I thought I would show you my efforts to date with the kind support and help of several of the forum members (my electronics skills are minimal!). To date I have completed of the all the pcb boards (see attached) but these have yet to be tested in anger (tomorrow).

I persevered with the 'fat' 6.8nF polyprops by mounting them on pcb pins above the resistors and attached them by winding a single copper wire strand to the capacator leg/pin and soldered accordingly. This took a long time and did try my temper to the limits when they would fall off just before soldering because the wire strand wasn't tight enough! Fishing forceps helped greatly to hold each end of the wire strands proud of the board and then the excess length cut off after soldering.

I also made the holes too large for the TO220 heat sinks on the pcb board, so I threaded the other side to take M3 screws.

Next stage..... building the case.

Regards

Rob

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Old 27th Mar 2010, 11:10 pm   #273
Andymic
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Default Re: The "Sussex" Homebrew Valve Tester.

Nice work Rob.

I never thought about leaving the edge of the board to mount a heatsing.

Andy
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Old 27th Mar 2010, 11:30 pm   #274
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi Andy and thanks.
It was my thought from the onset to mount the heatsinks on the board I just hope that they don't get too hot and warp the board, althought the board is relatively thick.

Regards

Rob
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Old 28th Mar 2010, 7:29 pm   #275
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi Rob
Well done nice neat work.
Keep an eye on how hot TR2 gets while testing valves. In the worse case it may have to dissipate up to 30 watts and I see that Mike used quite a substantial heatsink.

Frank
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Old 28th Mar 2010, 8:28 pm   #276
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi Frank and thanks,
I wonder if it is worth considering a localised fan akin to pc processor for direct cooling and heat discipation?

Regards

Rob
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Old 28th Mar 2010, 8:43 pm   #277
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi Rob
It's something that I have never tried in a project, but I fitted one once over a graphic card heatsink in a computer and it helped a lot.

Frank
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Old 29th Mar 2010, 12:56 am   #278
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi Topcap & Swordholder,

In testing the oscillator board and noting that it it is not responding as it should, in checking the board over for obvious faults I have noted that orientation of the electrolytic C8 has changed in the latter circuit diagrams. Is this a slip of the mouse (in todays terms) and that the original diagrams are indeed correct (I must brush up on my electronics ASAP).

Regards and Thanks

Rob
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Old 29th Mar 2010, 11:00 am   #279
swordholder
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Default Re: The "Sussex" Homebrew Valve Tester.

Rob
This may also be help to others having difficulty with the oscillator.
The voltages around the oscillator on my tester are:-
TR6 Coll -3.25v Base -0.66v Emit -0.04. VR1 set to 85R
TR7 Coll -8.45v Base -3.04v Emit -2.38v
The positive of C8 goes to VR2
Hope this helps

Mike
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Old 29th Mar 2010, 11:11 am   #280
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Default Re: The "Sussex" Homebrew Valve Tester.

Hi Mike,
Thanks for the reply and I checked the circuit diagram again this morning and my C8 is correctly placed. I assume that the circuit is initially tested with the 9v battery - 9v across the 0v input (designated as pin AB by Top Cap) and 0v (negative) across the negtive connection of C3 through a 47R resisitor. If this is correct I should be reading the voltages that you indicated across TR6 & 7.

I'll give it a try.

Regards

Rob
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