BC 221 Frequency Meter tidy up

[Rod Salter]

Mike,

I am pleased you have the power supply for yours.
I may use mine in a field display sometime, so I went for a battery version.

I agree with you that crystals drift off frequency,
In fact, I think this drift is why the Frequency Meter was invented perhaps?

scan bc2210001.jpg
Mine has no crystal in it.
The switch is set to xtal off, which bypasses the inner grid circuit to ground.
I, therefore, am unable to check the calibration, however, it seems accurate with this book.

Considering their age our units are doing well.

Somebody was very clever to find a book to match this unit.
Even the case is a mismatch.

I would like to know or see a photo of the 1000kc crystal if anyone has one? Please?

[Rod Salter]

BC221 PSU-9160 sm.jpg

I found a picture of a power supply

This brings me to another question seeing the circuit attached inside the battery compartment.

Mine does not have that one except there are holes where it could be attached.

My question, -- There are holes in the front lid, what are they for?
Are they for a card with instructions for use?

I have scoured the WWW for an open photo, but always they have the book displayed, covering up any writings that may be attached there

[Bruce MacMillan]

Nice bit of work!

The crystal in these units looks identical to the black valves. It has the same base as the valves.

If the holes are in the outside centre of the fold down lid they are for a data plate. It enabled the set to be identified without opening it up.

The term "meter" applies to a device that measures. Instead of a panel meter displaying visual info this unit gives aural output via the headphones.

[Jesse Browning]

The crystal unit looks identical to the other metal cased tubes except for the markings. What kind of holes are in the lid? Jesse.

[Rod Salter]

12.jpg

The front has 6 holes

I do not know what they held either inside or out.

Thanks for the information on the crystals, fellows,

Please, Anyone, have a photo of those crystals markings?

.

[David Dunlop]

Rod.

On my meter, the 6 holes you asked about are where a set of solid head, hollow rivets secure the metal backing plate for the calibration chart booklet to the front cover.

You mention your charts are not matched to the meter so I am guessing somebody at some point went to a lot of trouble to remove the original chart book from the meter.

Hope that solves your mystery.

David

[Bruce MacMillan]

The 6 holes should line up with the aluminum backing plate to the calibration book, BC221a. BC221b is the crystal and it is mounted underneath at a right angle, much like the valve on the other side.

[Rod Salter]

Thanks, David,
Thanks, Bruce, I would have never dreamed that a crystal could be in a metal valve.
I have some old metal valves that have lost their markings and maybe with open filament
I may think of using one to make a look-a-like crystal or maybe they are the crystal
I will plug them in and see if they oscillate before commencing surgery

Visitor here this morning can make decals to apply to it

He can print, redo dashes, radio fronts and who knows what else

I had forgotten about his business as I hadn't seen him for 2 years
Apparently, he and his motorbike found a landcrusier running a red light, He got banged up pretty bad and only just getting about again