BC221 frequency meter overhaul. - UK Vintage Radio Repair and Restoration Discussion Forum

Tyso_Bl · 25th Jun 2019, 11:13 pm

Picked one of these up at Newbury last Saturday. Looks tidy enough on the outside, the seller did make an effort to clean it up.

Inside is not too bad, except for corrosion to the tuning capacitor and the trimmer capacitors. The crystal switch and band switch shafts have seized where they come through the front panel, the tuning shaft bearings are also notchy, prolly hard grease, looks like damp storage and condensation got to it.

The question is I can't work out how to dismantle the thing (non destructively) in order to get to the bits that need attention. I can;t even work out in what order the thing was assembled.

Has anyone some pointers for me? Otherwise I may try the take out all the screws, and desolder all the wires approach, but that way may lie an unfinished project.

T

mickm3for · 26th Jun 2019, 12:00 am

Hi manual here http://www.rkk-museum.ru/documents/a...s/58-44-01.pdf hope this helps from memory 4 screws in front then it slides out of case

usradcoll1 · 26th Jun 2019, 2:04 am

Quote:

Originally Posted by mickm3for

Hi manual here http://www.rkk-museum.ru/documents/a...s/58-44-01.pdf hope this helps from memory 4 screws in front then it slides out of case

I always marveled at those instruments when I first started collecting. At present, I have about six of them, all different versions.
Philco had to come out with their own version, using their wonderful Loctal valves.
I incorporated a simple modulator using a Neon lamp. A circuit taken from a surplus conversion manual of the day.
Naturally, I built an AC mains power supply, which everyone seemed to do.

Herald1360 · 26th Jun 2019, 9:54 am

I hope it was free or nearly- nice though they are, even good ones don't fetch much

Brased · 26th Jun 2019, 4:11 pm

Remember that each instrument was individually calibrated - I assume that yours has its proper calibration book in the drop down front panel. Disturbing things may upset the calibration.

Edward

Terry295 · 26th Jun 2019, 8:44 pm

Hi Tyso

I read your post and would like to share an experience of an issue that can affect this equipment. I have one of these instruments and precisely because "looks like damp storage and condensation got to it", the acetate film windows in front of the "thousands" dial and calibration book developed "vinegar syndrome." This is where the film breaks down, shrinks and releases acetic acid. This caused significant corrosion to all metal parts on the front panel and took an age to rectify, this breakdown is accelerated and made worse if it is stored in a warm environment. I hope this hasn't happened to your 221, but it's as well to be aware that it can.

Regards Terry C (ZL4TC)

G6Tanuki · 26th Jun 2019, 9:45 pm

Quote:

Originally Posted by Brased

Remember that each instrument was individually calibrated - I assume that yours has its proper calibration book in the drop down front panel. Disturbing things may upset the calibration.

Edward

That's truly the big problem with any ageing-towards-senility frequency-calibration instruments.

Though they may have been useful for a decade or so after original-manufacture-and-calibration, components age and so the original calibration-graphs/books become deeply-untrustworthy.

And you'll find it really hard to find a UKAS-accredited calibration/test facility who knows what a BC221 is, let alone be prepared to take it on to do a proper reference-traceable calibration project.

IMHO better to treat your BC221 as a bit of antique electronica rather than aiming to use it as a day-to-day test-instrument!

Radio Wrangler · 26th Jun 2019, 10:42 pm

The BC221 cal charts were measured and printed automatically, page by page, then the pages were collated into a sort of loose-leaf binding. Incredible manufacturing technology for the day.

Over the years, I did get a couple that were being flung out, to save the drive mechanisms and the capacitor. They make awfully fine drives for VFOs.

David

M0FYA Andy · 27th Jun 2019, 9:15 am

This link gives some information on the original calibration charts -
http://jproc.ca/ve3fab/bc221.html
And this one is to software to make your own -
https://www.royalsignals.org.uk/arti...prog/index.htm
I'm not recommending this software as I've never used it, but it might be of use if you don't have the original charts.

Andy

avocollector · 27th Jun 2019, 8:21 pm

I have one of those 221's with the seized front band switch - on the roundtuit pile for now precisely because of that problem so great to see the info here. Given the solidity of the construction I would hate to have been one of the people ordered to destroy it when the enemy were coming!!!

Tyso_Bl · 1st Jul 2019, 12:15 am

Thank you all for the replies, especially the links to the extra info, most interesting. Well the original idea was to get one to canibalise for the tuning gear, I've been aware from other peoples projects that they are rather nice, they are too.

There was a choice of three at the rally, so I bought the last one I walked by, It was a fiver, so I'll get my moneys worth whatever I do with it. Having got it back to the bench I found that the tuning cap is very corroded/rusted, so any calibration will be well off if I do repair it, it would need extensive dismantling to get it out and clean. No real point is there? There are still loads of them about so I plan on getting a better cared for example some day.

Back to plan A.
I think there is the potential to turn this into a nice one or two band self contained QRP CW transceiver, plenty of room in the box so I'm going to have a go. The issue of non destructive disassembly is not too much of a problem now, which was what I was originally worried over.

I hope no-one takes issue with me doing this, but at least I'm not going to table lamp or steampunk it. Had it been in better condition I would have gone with plan B and overhauled/restore it.

The surplus parts will be made use of eventually, the Xtal will live on as a calibration marker.

I did turn an Advance sig genny into a regenerative receiver a while back, works OK and was an interesting project for a few weeks of spare evenings.

T

Tyso_Bl · 7th Jul 2019, 11:59 pm

Hmm, this may be a lost cause, not had to sort one out this bad before...

Tyso_Bl · 14th Jul 2019, 9:07 pm

Following on from the previous post, I've managed to get the gearbox mostly disassembled, so the things that are getting me stuck now are:

1, How do I derust the tuning capacitor plates?
2, How do I get the worm gear out of the box housing, I've loosened the set screws, the shaft is a very tight rotational fit in the wormwheel, I don't want to break anything with missaplied force.

3, The worm shaft, the part that the tuning knob is attached to, (it it called a boss), again loosened the set screws, but it won't come off...

help please?

T

25th Jun 2019, 11:13 pm	#1
Tyso_Bl Hexode Join Date: Jul 2014 Location: Magor, Monmouthshire, Wales, UK. Posts: 436	BC221 frequency meter overhaul. Picked one of these up at Newbury last Saturday. Looks tidy enough on the outside, the seller did make an effort to clean it up. Inside is not too bad, except for corrosion to the tuning capacitor and the trimmer capacitors. The crystal switch and band switch shafts have seized where they come through the front panel, the tuning shaft bearings are also notchy, prolly hard grease, looks like damp storage and condensation got to it. The question is I can't work out how to dismantle the thing (non destructively) in order to get to the bits that need attention. I can;t even work out in what order the thing was assembled. Has anyone some pointers for me? Otherwise I may try the take out all the screws, and desolder all the wires approach, but that way may lie an unfinished project. T __________________ Adapt, Improvise, Oh Bother.....

26th Jun 2019, 12:00 am	#2
mickm3for Heptode Join Date: May 2015 Location: Chatham, Kent, UK. Posts: 962	Re: BC221 frequency meter overhaul. Hi manual here http://www.rkk-museum.ru/documents/a...s/58-44-01.pdf hope this helps from memory 4 screws in front then it slides out of case

26th Jun 2019, 9:54 am	#4
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: BC221 frequency meter overhaul. I hope it was free or nearly- nice though they are, even good ones don't fetch much __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

26th Jun 2019, 4:11 pm	#5
Brased Hexode Join Date: Mar 2005 Location: London, UK. Posts: 318	Re: BC221 frequency meter overhaul. Remember that each instrument was individually calibrated - I assume that yours has its proper calibration book in the drop down front panel. Disturbing things may upset the calibration. Edward

26th Jun 2019, 8:44 pm	#6
Terry295 Tetrode Join Date: Nov 2009 Location: Christchurch, New Zealand Posts: 64	Re: BC221 frequency meter overhaul. Hi Tyso I read your post and would like to share an experience of an issue that can affect this equipment. I have one of these instruments and precisely because "looks like damp storage and condensation got to it", the acetate film windows in front of the "thousands" dial and calibration book developed "vinegar syndrome." This is where the film breaks down, shrinks and releases acetic acid. This caused significant corrosion to all metal parts on the front panel and took an age to rectify, this breakdown is accelerated and made worse if it is stored in a warm environment. I hope this hasn't happened to your 221, but it's as well to be aware that it can. Regards Terry C (ZL4TC)

26th Jun 2019, 10:42 pm	#8
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,857	Re: BC221 frequency meter overhaul. The BC221 cal charts were measured and printed automatically, page by page, then the pages were collated into a sort of loose-leaf binding. Incredible manufacturing technology for the day. Over the years, I did get a couple that were being flung out, to save the drive mechanisms and the capacitor. They make awfully fine drives for VFOs. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

27th Jun 2019, 9:15 am	#9
M0FYA Andy Nonode Join Date: May 2007 Location: Preston, Lancashire, UK. Posts: 2,511	Re: BC221 frequency meter overhaul. This link gives some information on the original calibration charts - http://jproc.ca/ve3fab/bc221.html And this one is to software to make your own - https://www.royalsignals.org.uk/arti...prog/index.htm I'm not recommending this software as I've never used it, but it might be of use if you don't have the original charts. Andy

27th Jun 2019, 8:21 pm	#10
avocollector Heptode Join Date: Jul 2010 Location: Wellington, New Zealand. Posts: 653	Re: BC221 frequency meter overhaul. I have one of those 221's with the seized front band switch - on the roundtuit pile for now precisely because of that problem so great to see the info here. Given the solidity of the construction I would hate to have been one of the people ordered to destroy it when the enemy were coming!!!

1st Jul 2019, 12:15 am	#11
Tyso_Bl Hexode Join Date: Jul 2014 Location: Magor, Monmouthshire, Wales, UK. Posts: 436	Re: BC221 frequency meter overhaul. Thank you all for the replies, especially the links to the extra info, most interesting. Well the original idea was to get one to canibalise for the tuning gear, I've been aware from other peoples projects that they are rather nice, they are too. There was a choice of three at the rally, so I bought the last one I walked by, It was a fiver, so I'll get my moneys worth whatever I do with it. Having got it back to the bench I found that the tuning cap is very corroded/rusted, so any calibration will be well off if I do repair it, it would need extensive dismantling to get it out and clean. No real point is there? There are still loads of them about so I plan on getting a better cared for example some day. Back to plan A. I think there is the potential to turn this into a nice one or two band self contained QRP CW transceiver, plenty of room in the box so I'm going to have a go. The issue of non destructive disassembly is not too much of a problem now, which was what I was originally worried over. I hope no-one takes issue with me doing this, but at least I'm not going to table lamp or steampunk it. Had it been in better condition I would have gone with plan B and overhauled/restore it. The surplus parts will be made use of eventually, the Xtal will live on as a calibration marker. I did turn an Advance sig genny into a regenerative receiver a while back, works OK and was an interesting project for a few weeks of spare evenings. T __________________ Adapt, Improvise, Oh Bother.....

7th Jul 2019, 11:59 pm	#12
Tyso_Bl Hexode Join Date: Jul 2014 Location: Magor, Monmouthshire, Wales, UK. Posts: 436	Re: BC221 frequency meter overhaul. Hmm, this may be a lost cause, not had to sort one out this bad before... Attached Thumbnails __________________ Adapt, Improvise, Oh Bother.....

14th Jul 2019, 9:07 pm	#13
Tyso_Bl Hexode Join Date: Jul 2014 Location: Magor, Monmouthshire, Wales, UK. Posts: 436	Re: BC221 frequency meter overhaul. Following on from the previous post, I've managed to get the gearbox mostly disassembled, so the things that are getting me stuck now are: 1, How do I derust the tuning capacitor plates? 2, How do I get the worm gear out of the box housing, I've loosened the set screws, the shaft is a very tight rotational fit in the wormwheel, I don't want to break anything with missaplied force. 3, The worm shaft, the part that the tuning knob is attached to, (it it called a boss), again loosened the set screws, but it won't come off... help please? T Attached Thumbnails __________________ Adapt, Improvise, Oh Bother.....