[Resto Diary] Radio Rentals Model Nr 217 (5 valves, mid 1950s)

[Gabester]

Hello everyone,

Welcome to a thread for my first valve radio restoration! Updates will be shared slowly, due to me breaking components as I learn about these wonderful devices.

I was surprised to find such a wealth of information on radio restoration online, so I will try to put all sources of information and schematics that may help others in similar journeys


Model: Radio Rentals Model 217 (as far as I found, it is the purchase version of the RR 210 in different case, also sold as the Baird 210 (schematics here). One example of a later (or more complex) version is the 8 valve Baird M218AC

Specifications: 3 Waveband 5 Valve Superhet 210W (1957?) 6 AM circuits

Provenance tale: from the kind seller in Wolverhampton area "It was from a distant family of family house clearance. The man collected all sorts of things and hoarded them well I must add. Went to auctions bought lots of unusual stuff from them so could be a little gem."

Photos on arrival and initial clean-up, with an old wrapper found inside (no sweets, though)

Cheers!

[PJL]

Is this an AC only set or AC/DC? If you are not sure post a picture of any information on the back panel.

[Gabester]

Hey, sorry forgot to upload images

[Gabester]

Some more progress record (first photos before cleaning, then proceeded to some testing).

The first issue (apart of no sound from speaker) was an overheating sizzling transformer with liquid epoxy flowing out of it. Reached +90C, its amazing how much these could take without dying. Output voltage was correct (300v each coil, plus valve heater and bulb supply). I replaced the rectifier valve EZ80, and it solved the overheating (probably a shorted valve? may check sometime later).

At this time I also replaced the 2 blown bulbs. Going with advice from this post, I got KL 6.5V 150mA instead of 300mA to keep brightness close to original bulbs (to recheck when I finish the radio).

For next steps, I will be replacing all electrolytic capacitors, one paper capacitor, and 3 resistors. The measuring log below for those interested:

Electrolytic capacitors
C39 and C35 (black ones)
Expected: 25uF
Measured: 83uF (away from the circuit) and 2uF (attached to circuit)

C41, 42, 43 (canned capacitors)
Expected: 16uF on all 3
Measured: 0,22,26uF

C40 paper capacitor (non-electrolytic)
Expected: 2nF
Measured: 5.1nF

Resistors
(all indicated 20% tolerance)

format: [id] [measured] (expected, deviation if high)

R1 10.1k (10k)
R2 1.55k (1.8k, -15%)
R3 28.9k (33k, -10%)
R4 42.2K (33k, +20%) (giant resistor)
R5 1.08M (1M)
R6 207 (180, +15%)
R7 202 (180, +15%)
R8 52.8K (47K, +10%)
R9 35.4K (33k)
R10 226 (180, +20%)
R11 100.5k (100k)
R12 NA
R13 48.8k (47k, +5%)
R14 48.8k (47k, +5%)
R15 48.8K to 800K (Volume control)
R16 >2M (2.2M) (off scale of multimeter)
R17 1.93k (1.8k)
R18 120k (100k, +20%)
R19 1.13M (1M, +10%)
R20 1.1M (1M, +10%)
R21 446k (470k, -5%)
R22 113k (100k, +10%)
R23 34k (33k)
R24 116k (150k, -20%)
R25 133k (470k, -70%) !
R26 138k (100k, +38%) !
R27 174k (180k, -5%)
R28 5.3k (3.3k, +160%) ! (located across capacitor can*)
R29 784k (750k, +5%)

*probably not the correct component, maybe an older repair

[Gabester]

Originally Posted by PJL

Is this an AC only set or AC/DC? If you are not sure post a picture of any information on the back panel.

Hi, I believe its AC only. If I understand correctly the circuit, there is only AC input (either 226-250 or 195-225 with the flap), no input for DC supply...

[Paul_RK]

Definitely AC only, or it wouldn't have the mains transformer: and a good choice to start with, not valuable but fairly unusual and well worth saving, and the circuit is probably quite standard and straightforward, both because it lacks the complications that come with FM and in that it's a rental model which usually meant designers were required to keep things simple.

Paul

[Gabester]

Quite right Paul, I lucked out on such a forgiving model. While it will probably not play much of AM, I will definitely try to use as part of the home stereo.

Attaching photos of the capacitors rebuild. The solder was not sticking to the rivets (maybe aluminium?), so I drilled a hole through and tied the wires around the pins before soldering over.

Good sources on can and paper capacitors rebuild:
1
2
3
4
5
6
7
8
9
10

[Gabester]

As the can was sliced at the base, I decided to run a ground wire down the base via a 600V-rated wire and attach to a chassis bolt.

[JoshWard]

I really like Radio Rentals sets. They are always solidly built and usually work well too. I don't think I have ever seen one quite like yours before. There appears to have been a lot of different cabinet variations using the same few chassis types! I look forward to seeing more.

[slidertogrid]

an excellent and detailed write up! You are making an excellent job of that.

I have a couple of RR sets in my collection an earlier one with octal valves and a much later one which I think was made by KB.