R107 muting pins.

[HMV 1120]

Just a quick note. I recieved an R107 set from Graham (llama) today. It is currently having a plug and lead change before instalation alongside the domestic sets.

I gather that the two left hand pins of the transmit muting socket are live whilst the set is on - what voltage is this (i.e. is it dangerous) and what is the best, least unsightly way to prevent accidental contact?

Edit: Second thoughts: I have here a set of 20,000 ohm headphones - are they suitable for use on this set, and what sort of headphones connector am I looking out for?

Re-edit: The set is wired up for an S-meter in place of the Watch holder - this is removed and the watch holder replaced, but the wiring is still there. Would putting an S-meter (non permanent) into the watch holder make a useful addition or would this degrade the sets value at all?

In all other respects it is in completely original, unmodified form.

Many thanks, Robs.

[Sean Williams]

Rob,

The Muting contacts are at full HT (250vdc)

Erm, It has a speaker, so not sure why you would want to torture your ears! - Phone connector is not a 1/4 inch jack plug - it is a telephone switcboard type plug.

As for the S meter, sure, rig it up - the R107 isnt that rare, nor is it hugely valuable - if the set is modified in any way, the value drops a little, but if the mod is done so it is reverseable then less harm is done.

Have fun, Mind the muting contacts!

Sean

[HMV 1120]

VMARS, here we come!! Will be listening in 'authentic style' this weekend. I was wondering about the headphones as I am in a dorm and my room mates don't want to be awoken by static at 8:30 on a saturday morning. I hawever want to fire up on HF and tune around before laptops (and their hash generating PSU's) get turned on.
Muting pins shall be taped over for now (I guess 250 V HT might hurt (!) ), and I'll want to make sure no inquisitive fingers find that out. You cannot garauntee another persons stupidity after all.

Will post a few photos once set up.

Cheers, Rob.

[Station X]

Do you have the circuit etc Rob? This set was designed to work into low impedance headphones, so the 20,000 ohms you quote seems rather high. The speaker output is 200mW into a 10 ohm speaker, so you might do better with a pair of personal stereo type headphones connected across the speaker output. Always take great care when using headphones with valve equipment though.

There is activity on the VMARS AM net 3.615 Mhz around 8:00AM most mornings and often around mid day as well.

[Keith]

High impedance headphones will be fine on a lower impedance output (although I suspect they are more likely to be 2,000 ohms than 20,000 ohms!).

[HMV 1120]

Another question regarding this set - the serial plate has the initials 'McMR' - I assume this means the set was built by the McMichael Radio company?

If anybody has picutres of one of these sets in it's original operating position I would be very grateful if they could post them.
Cheers, Robs.

[MichaelR]

Believe it or not they were used at Arnhem.

Mike

[Sean Williams]

The R 107 was used in a number of different situations - It was used with the monstrous WS53, as well as the very heavy WS12 (this set looks as if it was the original companion transmitter)

There are a number of accessories used with the 107, depending on the setup.

You would find the set mounted in the back of a Bedford QLR as part of a command vehicle setup. Wireless for the Warrior has several references to the set.

HTH
Sean

[HMV 1120]

Pic of the set here:
http://www.imagestorer.com/images/Dd...scf0122mod.png

All the dials need new markings. The mains chord has been replaced.

[Royboy]

I used one of these sets during my Royal Signals service- 1951 to 1956.
If the switch to the right of the muting pins is switched on then the pins are live - very alive - The knuckles of an unwary hand grasping the left-hand grab handle was sure to touch the pins - usually only once!
It must have been an idiot who designed the muting connection this way.
The sensible way to do it would have been to fit a socket not a plug.
I know that a blanking plug should have been fitted when the muting system was not used but I never saw a 107 which did not have this item missing.
The best thing I can say about this receiver is that it was very robust.
Royboy

Tune for maximum smoke! Old signals saying.

[MichaelR]

Originally Posted by Royboy

It must have been an idiot who designed the muting connection this way.
.

Perhaps the designer misread the spec and was aiming to mute the operator

Mike

[McMichael]

Originally Posted by HMV 1120

Another question regarding this set - the serial plate has the initials 'McMR' - I assume this means the set was built by the McMichael Radio company?

As far as I know (from the McMichael history booklet written in 1979) R107s weren't made by McMichael, but I am quite happy to be corrected on this. I have done a brief search using Google but I can't find any info as to who did make them. Amongst a whole lot of various other things, McMichael made receiver sections for the HF Transmitter/Receiver Type WT11 for use in tanks and other vehicles, together with test gear for servicing, and the aircraft Receiver Type R1125. The company also produced the receiver (B2) for a small suitcase transmitter/receiver which was dropped into Occupied Territories for use by the local Resistance movements.

David

[Station X]

As far as I know the R107 was manufactured by "Radio Transmission Equipment Ltd" and "Ferguson Radio Ltd". The label described could denote McMurdo.