Wayne Kerr Autobalance Universal Bridge B642 - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

Radio Wrangler · 20th Jan 2013, 9:20 pm

It makes getting a resistor easier, but then you need a 6 digit DMM to measure it!

If you do a 4 wire Ohms measurement on a 1% metal film resistor before you use it on the B642, and do it again afterwards and get the same result, then you can reasonably assume the resistor wasn't different in the intervening time.

It's easier to hire a precision DMM for a day than to hire a resistance standard.

THe capacitor is still the bugbear. Sometimes 'Sullivan' standard capacitors turn up, but they're usually old and of unknown history.

Sorry
David

Camino1 · 22nd Jan 2013, 8:43 pm

Thanks to the help of Tim and Woodchips I will soon have the 0,01% resistors and a 0,5% capacitor. A Dutch ham nearby, with the right testequipment will help me to measure with the accuracy that I need.
It is amazing what this Forum can do for you!
I have been looking for General Radio standard capacitors. Price at least $195,- accuracy 0,02%. Does anyone know an alternative? The G.R. capacitors are silver-mica. For long term stabilty and low tempco is teflon a good choise?

Henk

Camino1 · 7th Feb 2013, 7:14 pm

Today Fred helped me by measuring the resistors and the capacitor. All better than 0,01%!!! Thank you very much for sending them Bob!
The bridge needed no calibration. Well within specs. 0,1%.
Again thanks to all forum members for helping me.

Henk

rodppereira · 29th Mar 2015, 7:15 pm

Quote:

Originally Posted by Camino1

Thank you all for helping me. Special thanks to Bob, Woodchips, who sent me his manual. Colins post was spot on: I will replace all R's with metal-film. Thank you Colin

Hi,

Do you have the B642 manual digitalized?

I acquired this Bridge too and I´m looking for the manual, until now without success. Maybe you can help me!

Thanks in advanced.

Regards,
Rodrigo.

Camino1 · 31st Mar 2015, 3:11 pm

Hi Rodrigo

Not digitized. I could scan it if you like.

Kind regards

Henk

Station X · 27th Oct 2017, 9:02 pm

The operating instructions and a circuit diagram are now available from the BAMA website:-

http://bama.edebris.com/manuals/wayne/b642

J.Stocking · 24th Nov 2017, 12:44 pm

Hello All,
I am new to this forum having just acquired a Wayne Kerr B642 Bridge in need of TLC.....I have the operating manual and a circuit diagram of the Oscillator but no maintenance or calibration info.
The bridge seems to set up OK except when it comes to setting the FSD on the 'C' meter. Adjusting the ' FSD' control only allows the meter needle to reach about 4 on the scale and the 'Zero' control seems to have very little effect on the 'G' meter. The Oscillator seems to be working OK.
I have no circuit diagram for the Bridge as a whole, only for the oscillator, and so am unable to see what cold be causing the problem.
Any help or ideas would be most welcome and a scan of the relevent circuit diagram ( which I would be willing to pay for) would be wonderful
Thanks & regards
John

20th Jan 2013, 9:20 pm	#21
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,870	Re: Wayne Kerr Autobalance Universal Bridge B642 It makes getting a resistor easier, but then you need a 6 digit DMM to measure it! If you do a 4 wire Ohms measurement on a 1% metal film resistor before you use it on the B642, and do it again afterwards and get the same result, then you can reasonably assume the resistor wasn't different in the intervening time. It's easier to hire a precision DMM for a day than to hire a resistance standard. THe capacitor is still the bugbear. Sometimes 'Sullivan' standard capacitors turn up, but they're usually old and of unknown history. Sorry David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

22nd Jan 2013, 8:43 pm	#22
Camino1 Retired Dormant Member Join Date: Nov 2012 Location: De Meern, Netherlands. Posts: 20	Re: Wayne Kerr Autobalance Universal Bridge B642 Thanks to the help of Tim and Woodchips I will soon have the 0,01% resistors and a 0,5% capacitor. A Dutch ham nearby, with the right testequipment will help me to measure with the accuracy that I need. It is amazing what this Forum can do for you! I have been looking for General Radio standard capacitors. Price at least $195,- accuracy 0,02%. Does anyone know an alternative? The G.R. capacitors are silver-mica. For long term stabilty and low tempco is teflon a good choise? Henk

7th Feb 2013, 7:14 pm	#23
Camino1 Retired Dormant Member Join Date: Nov 2012 Location: De Meern, Netherlands. Posts: 20	Re: Wayne Kerr Autobalance Universal Bridge B642 Today Fred helped me by measuring the resistors and the capacitor. All better than 0,01%!!! Thank you very much for sending them Bob! The bridge needed no calibration. Well within specs. 0,1%. Again thanks to all forum members for helping me. Henk

31st Mar 2015, 3:11 pm	#25
Camino1 Retired Dormant Member Join Date: Nov 2012 Location: De Meern, Netherlands. Posts: 20	Re: Wayne Kerr Autobalance Universal Bridge B642 Hi Rodrigo Not digitized. I could scan it if you like. Kind regards Henk

27th Oct 2017, 9:02 pm	#26
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Wayne Kerr Autobalance Universal Bridge B642 The operating instructions and a circuit diagram are now available from the BAMA website:- http://bama.edebris.com/manuals/wayne/b642 __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

24th Nov 2017, 12:44 pm	#27
J.Stocking Diode Join Date: Nov 2017 Location: Melton Constable, Norfolk, UK. Posts: 1	Re: Wayne Kerr Autobalance Universal Bridge B642 Hello All, I am new to this forum having just acquired a Wayne Kerr B642 Bridge in need of TLC.....I have the operating manual and a circuit diagram of the Oscillator but no maintenance or calibration info. The bridge seems to set up OK except when it comes to setting the FSD on the 'C' meter. Adjusting the ' FSD' control only allows the meter needle to reach about 4 on the scale and the 'Zero' control seems to have very little effect on the 'G' meter. The Oscillator seems to be working OK. I have no circuit diagram for the Bridge as a whole, only for the oscillator, and so am unable to see what cold be causing the problem. Any help or ideas would be most welcome and a scan of the relevent circuit diagram ( which I would be willing to pay for) would be wonderful Thanks & regards John