Valve radio repairers?

tc20

Hi all,
im looking for a bit of help or info on where i can get an old radio up and running again. It came into my ownership a couple of months ago, and i've been meaning to get round to it.
Its a Bush, AC mains receiver, Type AC81. Cant tell how old it is. The cabinet is about 2foot wide, a foot tall, and 10 inches deep. It has the A-Z listing of old european radio centres on the dial, and when plugged in, the backlight illuminates, but no sound There a 4 knobs on the front, going from left to right they do the following-
On/off/volume
Dont know
Tune
Switch bands (by turning this last knob, it illuminates each band on the vertical strip MW/SW/LW)

To the rear, apart from the mains lead, there are 3 ports-
One for aerial and earth
Int LS and Ext LS (loudspeaker)
Pick up

Im wondering if anyone knows of repair shops, or individuals with an interest in these old radios who might be able to fix it. I did email the Irish HAM radio club, but got no reply. Im in north wicklow.
Cheers

gyppo

Would it be this model??

http://www.jhorne62.freeserve.co.uk/radio/bush_dac81.htm

RoundyMooney

I'm a valve radio buff, but unfortunately you're a bit far away!

It sounds like a DAC 81 alright, a conventional enough set, from the late forties. This is an AC/DC radio, so the chassis may become live. PROCEED WITH CAUTION!

First off, that mystery control is "Tone".

The main issue with them is dampness, in that the capacitors within (electronic components, if you didn't know) will soak up moisture to the point that they do not function correctly anymore. In electronic terms this is known as "leakage" and can happen even in a dry environment. The only option is to replace them with modern equivalents, in some instances when restoring, the old capacitors are "restuffed" with the new, which are much smaller and hence the set looks original under the chassis. There will be 40ish in a set like the DAC81, and you can guarantee that some will be bad. They can be left alone if the radio works, but I wouldn't do it. The main reason being that valves can be damaged, and are considerably harder to acquire, although not impossible. Yet.

Valves themselves tend not to give trouble, but there are a few things you can do before we move on.

Turn the set on, and have a look in the back (without touching the chassis!). Do all five valves and the dial light up? If not you probably have a problem with the heater circuit. Try the three wavebands in the same manner.

Let us know how you get on, before you go any further.

Thanks.

tc20

Thanks lads,
@ gyppo - yeah, it looks similar to that one in the link.

@ Roundy - great info thanks. Whereabouts are you based? I have heard the sound from a friends old (Grundig i think) radio in Germany...boy is it a lovely 'rich' sound if you know what i mean. My father in law retired last year from the antiques trade, (Edward Butler Antiques on Bachelors Walk) and he gave me the radio. His normal line of stock was furniture and items with a nautical connection (ships binnacles/naval instruments etc) so he didnt have much info on the radio, just something he picked up along the way.
I'll have a look at the innards later this evening and let you know how i get on

edit - i see you're in the PRC Roundy, boy!

RoundyMooney

I am indeed

Valve equipment has what is termed as a "warm" sound. I'm after a nice vintage guitar amp at the moment for just that reason, but that's another story...

The biggest issue (for now) is that there's llareggub on the AM bands anymore.

There are aftermarket AM transmitters available in the US which can be hooked up to an audio source such as a PC or mp3 player. As far as I know they're illegal in this country so, you understand, I couldn't recommend them...

I think I remember that shop, now that you mention it.

gyppo

As Roundy said, be very cagey around old valve sets - they have a tendancy to straighten your hair if you're not careful.
Often, old sets like these have been subject to damp at some stage, and tend to have corroded valve seat connections. Removing and replacing each valve in turn a few times (with the unit powered off) can sort out many contact problems.

tc20

Ok lads, this is what i saw when i took off the back card last night -
a lot of cobwebs for a start, then the chassis (which takes up about 2/3rds of
the width of the cabinet, open at both ends. On the top deck, 2 glass cylinders, a bit like lightbulbs (are these the valves?), 3 red cylinders (shaped like bullet/shell casings) about 4" high, 2 of which are topped with round metal caps c.1" diameter. Also 2 fat metal cylinders. A transformer of sorts with a twisted pair going to the speaker (speaker is a ROLA Type 8 - Z ).
One other square housing with what looks like flat rolled black "stuff" in the housing. On top of this housing are the digits "210 230 250", so a choice of voltages i assume. Theres a knurled screw in the 230 spot.
Had the unit powered up with the back off, and was VERY careful not to touch anything. I am very wary around electricity anyways.
Only the dial lit up, no valves (im assuming the lightbulb looking yokes are the valves)
Cant see much of the lower deck, except on the right hand open end, where there is a a board with about 15 caps & resistors. I can make out a large metal cylinder but not much else.
When i changed the bands, with power on, this is what i noted-

Band 1 wavlength 900-1900
from "Aircraft" to "Kaunas"

Band 2 wavelength 20-50
Vatican City to Moscow

Band 3 wavelength 200-550
Dublin to Wilno

Knob all the way to the left iluminates the strip for band 1 (im waiting for the knob jokes lads :rolleyes: )
Then there seems to be an intermediate 'off', by turning knob to the right.
Turn it right again and it illuminates the strip for band 2.
Knob doesnt go any further to the right, so band 3 does not illuminate.

There was also a card "Inspection label" fixed to the inside right of the cabinet with the following handwritten "1st mechanical insp. 11/12/46" and also the 1st electrical test on same date.
Also a "Royalty Plate" in what looked like faded white/cream bakelite

I havent touched any of the innardsso far, to avoid new hair-do's, but theres no internal power source is there? So i'd be safe to delve into it as long as its unplugged?

Any thoughts, or next steps welcomed

RoundyMooney

I'll take this piece by piece. It'll probably make more sense (to me at least!) that way. The advice below assumes that the radio hasn't been "modified" in any way...

tc20 wrote:

Ok lads, this is what i saw when i took off the back card last night -
a lot of cobwebs for a start, then the chassis (which takes up about 2/3rds of
the width of the cabinet, open at both ends.

Good stuff.

tc20 wrote:

On the top deck, 2 glass cylinders, a bit like lightbulbs (are these the valves?),

Two of them, yes. Rectifier and Audio output (for those who know).

tc20 wrote:

3 red cylinders (shaped like bullet/shell casings) about 4" high, 2 of which are topped with round metal caps c.1" diameter.

These are also valves, (frequency changer, I.F. amp, and audio pre-amp/detector/AGC). The red stuff provides screening from interference.

tc20 wrote:

Also 2 fat metal cylinders. A transformer of sorts with a twisted pair going to the speaker (speaker is a ROLA Type 8 - Z ).

The fat metal cylinders are I.F. (Intermediate Frequency) transformers. You don't need to worry about these. The latter is also a transformer (for audio output). Once the wiring is intact, you'll probably have no worries here either.

tc20 wrote:

One other square housing with what looks like flat rolled black "stuff" in the housing. On top of this housing are the digits "210 230 250", so a choice of voltages i assume. Theres a knurled screw in the 230 spot.

Correct. This is a dropper resistor for voltage selection.

tc20 wrote:

Had the unit powered up with the back off, and was VERY careful not to touch anything. I am very wary around electricity anyways.
Only the dial lit up, no valves (im assuming the lightbulb looking yokes are the valves)

Are you sure about that? From the diagram I have, the pilot lamp shouldn't come on at all if the valves aren't making contact or have blown filaments.

tc20 wrote:

Cant see much of the lower deck, except on the right hand open end, where there is a a board with about 15 caps & resistors. I can make out a large metal cylinder but not much else.

This is an electrolytic capacitor. I'd suspect it as well.

tc20 wrote:

When i changed the bands, with power on, this is what i noted-

Band 1 wavlength 900-1900
from "Aircraft" to "Kaunas"

Long Wave.

tc20 wrote:

Band 2 wavelength 20-50
Vatican City to Moscow

Short Wave.

tc20 wrote:

Band 3 wavelength 200-550
Dublin to Wilno

Medium Wave (or A.M.)

The numbers refer to the wavelength in metres (just another way of saying frequency).

tc20 wrote:

Knob all the way to the left iluminates the strip for band 1 (im waiting for the knob jokes lads :rolleyes: )
Then there seems to be an intermediate 'off', by turning knob to the right.
Turn it right again and it illuminates the strip for band 2.
Knob doesnt go any further to the right, so band 3 does not illuminate.

Yep, your pilot bulb is blown for Band 3 (MW), so the valves will not light in that position anyway.

tc20 wrote:

There was also a card "Inspection label" fixed to the inside right of the cabinet with the following handwritten "1st mechanical insp. 11/12/46" and also the 1st electrical test on same date.
Also a "Royalty Plate" in what looked like faded white/cream bakelite

Imported radios of that era were subject to importation duty. Some manufacturers got around this by assembling here (even cars!). This set was subject to duty and so was UK made I imagine.

tc20 wrote:

I havent touched any of the innardsso far, to avoid new hair-do's, but theres no internal power source is there? So i'd be safe to delve into it as long as its unplugged?

The capacitor I referred to above may hold a charge, but not a lot. Wait ten minutes after unplugging and you should be ok.

tc20 wrote:

Any thoughts, or next steps welcomed

Make sure ( in a darkened room) that those valves aren't heating when the pilot lamp for each band is on. After that, come back to us.

tc20

Cheers Roundy..
in relation to where you say am i sure that nothing lit up... well i was looking into the cabinet, power on, and two separate bulbs came on (one at a time) when i turned the knob for changing bands. Checked by looking at the front of the cabinet, and confirmed that these bulbs were same that lit the bandwidth dials.
I was looking at the radio around 9.15pm, so fading light (i had a miners headlight on). I'll do the same, as you suggest, but when room is in darkness and see if there's any sign of life in the valves. I'll give em a good de-webbing and twiddle, without the power of course beforehand.
I'll let you know what gives on monday (no PC at home, so i'm supposed to be working here!!)

RoundyMooney

Well tc, any luck?

I hope you didn't singe your fingertips or anything?

tc20

Roundy, im typing this from the burns unit of the local hospital... nah, just kidding..
I had another look at the radio last night, and this is the update..
Without power, i twiddled and pulled at the valves. Not wanting to be too forceful in case i broke 'em, i discovered that they lift out.
The smaller of the two valves is marked "Mullard CY 31", the larger is a Mullard CL33. Filaments are gone in both. (sounds like a blown light bulb when you give it a rattle)
Both valves have 8 hole conns on the bottom, arranged circularly. The smaller valve has 6 pins, the larger has 7 (ie 2blanks on the sml, 1 on the lrg)
and both have a central, plastic?, pin.
Both valves,altho still clear glass, have in places an apperance of 'mirroring' if you get where im coming from.
The two red valves which are topped with 1" metal covers, well i lifted off the caps and found 1 resistor in each. These 2 valves, and the other red one (freq. changer, IF amp and the other one) all seemed to be secured to the top deck of the chassis by other means, so i left them be.
Then with power on, i waited, but no apparent heat from any of the valves, tho an electrical hum was present. I guess this is just from the pilot bulbs which light up the bandwidth display.

So thats the latest, im off on me holliers for a week in the sun tomorrow, so i'll catch up when i get back. If you think of any more 'homework' for me, let me know.

cheers

RoundyMooney

tc20 wrote:

Roundy, im typing this from the burns unit of the local hospital... nah, just kidding..
I had another look at the radio last night, and this is the update..
Without power, i twiddled and pulled at the valves. Not wanting to be too forceful in case i broke 'em, i discovered that they lift out.

They all do. They're fitted in 8 pin (octal) sockets IIRC.

tc20 wrote:

The smaller of the two valves is marked "Mullard CY 31", the larger is a Mullard CL33. Filaments are gone in both. (sounds like a blown light bulb when you give it a rattle)
Both valves have 8 hole conns on the bottom, arranged circularly. The smaller valve has 6 pins, the larger has 7 (ie 2blanks on the sml, 1 on the lrg)
and both have a central, plastic?, pin.
Both valves,altho still clear glass, have in places an apperance of 'mirroring' if you get where im coming from.

The mirroring is perfectly normal and is part of the manufacturing process. The rattle test is not a sure thing when it comes to valves, as there's a lot in there to move around! I would assume that the valve filaments are ok, as they're an integral part of the circuit feeding the dial lamps (which work).

Do you have access to a multimeter,and know how to use it? There are a few "dead" checks you can do, not least on the valves themselves if so. Pins 2 and 7 are the heater(filament) connections on all these valves and should show a relatively low resistance if the heaters are ok.

tc20 wrote:

The two red valves which are topped with 1" metal covers, well i lifted off the caps and found 1 resistor in each. These 2 valves, and the other red one (freq. changer, IF amp and the other one) all seemed to be secured to the top deck of the chassis by other means, so i left them be.
Then with power on, i waited, but no apparent heat from any of the valves, tho an electrical hum was present. I guess this is just from the pilot bulbs which light up the bandwidth display.

Hum through the speaker? How loud?

tc20 wrote:

So thats the latest, im off on me holliers for a week in the sun tomorrow, so i'll catch up when i get back. If you think of any more 'homework' for me, let me know.

cheers

Enjoy the break!

tc20

Hey Roundy,
i know how to use a multimeter alright, and should be able to cadge one from somebody for a day or two.
Is Pin #1 marked as such, or is it trial and error? And would trying the valves in different pin locations do anything? Im just wondering in case a previous owner had fiddled with them, and perhaps not put them back in the correct location..
As regards the hum im not that sure it was coming thru the speaker, it seemed to be from a component, or possibly the power source that was illuminating the pilot bulbs.

And cheers, i'll enjoy the break.

RoundyMooney

Layout number 3 on this page (same as the diagram for 2) is what you're after:

Link.

The valve layout is ( I assume from L to R, or from the end opposite the mains lead going in): CCH35, EF39, EBC33, CL33, CY31. The first three of these are the red valves with top caps, and the last two are your glass jobbies.

The fact that you can use a multimeter helps, as you may be able to do a fair bit of the diagnosis yourself.

The next question really is, how far you want to go with this under your own steam? If you want to attempt a repair yourself, it's possible, but you'll have to (with our help of course) immerse yourself in obsolete technology and terminology, and probably learn an awful lot of useless (to the vast majority of people) information. Now that's not a bad thing, but if you just want to get the radio working again, you'll probably need to get it to an enthusiast if it turns out to be an under chassis fault, which my gut feeling tells me it probably is.

If it comes to that, if you can get the set to me at some point, I'll be happy to get it running if at all possible, but that's an option we may not need to take.

tc20

Hey Roundy,
thanks for all your input so far.. tbh i think i'd be willing to pass the radio on to get it up and running. Im not shying away from having a go meself, just a lot on the plate at the mo - starting an extension this week, and trying to coax my old merc back on the road again are taking priority.
I know this is a bit of a 'how long is a piece of string' question, seeing as we dont know exactly whats wrong, or if its viable at all, but how available are the components, or is there a bit of homemade jiggery-pokery involved too?

watty

If you know where to look all the parts are available. Oddly the valves can be easier to get than some high voltage capacitors.

These are fairly simple and very easy to fix compared with any radio from 1980s to now.

It's harder to get a custom replacement IC for a 1990's radio. (The consumer Philips ICs aren't too bad)

RoundyMooney

What watty said, basically.

Discrete components of the correct spec are not too hard to come by at all, and Russia and China are still happy hunting grounds for valves, even though the more common types are not as rare as you might think.

tc20

PM sent

pilslager

PM sent, ah lads cmon, dont leave us hangin. What was the outcome, did you get the radio fixed.

RoundyMooney

Myself and tc20 haven't had an opportunity to touch base as yet, but I'm going to get the beast running for him, at which point I think he intends to restore the cabinet. Either way, it's another old radio saved.

pilslager

Thats great news, fair play roundy, keep us informed on the progress and maybe put up a few piccies of it. I would love to see it in the flesh.

Jerrk001

Hiya, Have an old Pye radio I'm trying to get up and running! Any idea where to start? Thanks.

RoundyMooney wrote: »

I'm a valve radio buff, but unfortunately you're a bit far away!

It sounds like a DAC 81 alright, a conventional enough set, from the late forties. This is an AC/DC radio, so the chassis may become live. PROCEED WITH CAUTION!

First off, that mystery control is "Tone".

The main issue with them is dampness, in that the capacitors within (electronic components, if you didn't know) will soak up moisture to the point that they do not function correctly anymore. In electronic terms this is known as "leakage" and can happen even in a dry environment. The only option is to replace them with modern equivalents, in some instances when restoring, the old capacitors are "restuffed" with the new, which are much smaller and hence the set looks original under the chassis. There will be 40ish in a set like the DAC81, and you can guarantee that some will be bad. They can be left alone if the radio works, but I wouldn't do it. The main reason being that valves can be damaged, and are considerably harder to acquire, although not impossible. Yet.

Valves themselves tend not to give trouble, but there are a few things you can do before we move on.

Turn the set on, and have a look in the back (without touching the chassis!). Do all five valves and the dial light up? If not you probably have a problem with the heater circuit. Try the three wavebands in the same manner.

Let us know how you get on, before you go any further.

Thanks.

watty

Tell us more about it and more about your level of technical expertise?

Jerrk001

Thank you for coming back to me. I'm afraid my level of technical expertise not great. However I do have power but no sound. When I took off the back of the radio the valves seemed to be working - one valve I am not sure of (it did get warm but no light). There are two controls on the front - one is the on/off dial with tone and volume, the other on the right hand side of the front takes you through the wavelengths. There is an indicator on the upper left front of the radio which does not light up - I imagine it should?

daltonrichard

Hello

Did you ever find out if there is anyone in Dublin who repairs valved radios. I also have a valved radio and need it repaired. I also live in Dublin. Thanks

watty

There is one Dublin guy that repairs valve radios on this Forum http://vintagetvandradio.myfreeforum.org/index.php

fraglerocks

Hi,

I have an old A168 radio I was going to refurbish. Where could I buy replacement valves, resistors, diodes, etc, if needed? Also, is the chassis of this model radio live when plugged in? I have a multimeter to check anyway but I just thought someone might know offhand.

Thanks.

watty

Do check C41 for leakage. If it's Hunts or waxed paper or tar coated replace.

It's not live chassis, but assume all sets are even when they are not.

The HT can kill, even stored on C43, C44, C45 for a short while after turning off.

Only power for a few minutes on / 5 off and check that C43, C44, C45 don't get hot. They may need to "reform" hence short operate times to start with.

Ebay for parts. If a valve lights up it usually works. Though gain drops with age. If not used for 20 years gain may be low on valves and improve dramatically after 20 minutes.

Join here for help
http://vintagetvandradio.myfreeforum.org/index.php

If you make a habit of this then join www.radiomuseum.org (which is NOT a forum)

It's very rare that resistors need replaced, but not unknown.

R23 could be 300K or 3M and it won't make much difference.
R27 +/- 10% as it sets the bias current. If the C42 is dried out the gain is low. If it's very leaky then bias current will be too high and risk damaging valve or transformer.

fraglerocks

Thanks Watty for the advice. I was going to start off with completely removing the chassis and cleaning it with cotton buds and ethanol and then leaving it in a dry atmosphere for a few days while I check the wooden case and treat it for woodworm if needed. Then I was going to replace whatever wires that look obviously worn and possibly mount a small internal antenna, reinstall the chassis and give it a run to see what happens... It hasn't been plugged in or turned on for at least 10 years and I can't remember if there was anything coming from it then.

There is a bit of rust on the main transformer, is it possible to clean it or should I just try to replace it in case it blows out?

PS, I'm not an electrician so I wouldn't know all the terminology but I have done a bit of meddling with control panels for pumps, motors, etc and a bit of domestic wiring in my time. Nothing has burnt down after and both myself and other people are still alive so I must be doin' a small bit right

watty

Rust on mains transformer doesn't matter. You can paint the rusty bits with Phosphoric Acid / Rustin's Rust Remover after brushing off loose material.

Don't power it at all with out replacing C41 if it's a tar or wax cardboard type (or a brown or black "Hunts" brand).

Only replace wire that the insulation has actually cracked off.


Do read
http://www.radiomuseum.org/forum/replacing_old_capacitors.html

Join a specialised Vintage forum like
http://vintagetvandradio.myfreeforum.org/index.php

brownmini

tc20 wrote: »

Hi all,
im looking for a bit of help or info on where i can get an old radio up and running again. It came into my ownership a couple of months ago, and i've been meaning to get round to it.
Cheers

try
http://www.crookedwood.com/Holmesaudio/Holmes_Audio.html

fraglerocks

Watty,

Thanks for the last advice. Attached are photos of the Murphy A168 chassis. As you can see wiring is a bit messy so its a bit hard to know what's what on the circuit diagram. Labelling is practically non-existent so I don't know what's what... Two of the capacitors (circled in red) seem to have leaked in the past. No info on them as to what they are rated. Also, two bulbs seem to be gone. I think they're 2V. The valve also circled has lost alot of its coating. Should it be replaced?

Have you any idea where C41 is on the chassis photos? What is its significance and why is it important for it to be changed?

watty

If C41 is leaky then the output transformer, output tube, HT dropper resistors are all having too much current. One or more fails!

The Audio Transformer and 6P25 output valve are more expensive to replace than buying a whole similar radio!

Start at Loudspeaker. It's driven by output transformer which connects between o/p valve (tube) anode pin and HT (200V to 275V DC ).

pin numbers are clockwise from underside.

The C41 connects to o/p valve grid pin.

It doesn't matter for now about the screening paint. You can use spray on nickel or tie on aluminium foil if it's a problem. Likely not

The large 6P25 is audio out
from underneath
Pin 1 to left of notch and pin 8 to right

Pin 5 is grid from R22 47K = Yellow Purple Orange, connected to C41 and R23 Yellow Purple Yellow.

Pin 3 is anode to audio out transformer

The C41 other end connect to 6LD20 Anode which is pin 2 (2nd pin clockwise underneath) and the anode has 100K = Brown Black Yellow connected.

so the pale yellow Dubilier vertical in the photo just to right of pair of cans is likely C41


Bottom Can is likely C29 4uF, upper C43 16uF. If there is a yellow purple orange resistor (47K) between them.

The bulbs are usually 6.3, 6.5 or 7V 100mA or 300mA. Never 2V anyway. 6.0V torch bulbs will last only days.

Trace out from 6P25 pins marking component designation on the photo.

Component codes
http://www.radiomuseum.org/forum/for_beginners_prefixes_and_codes.html

Note that "unused" valve (tube) base connections are often used as "connection tags" to hang parts that might not even connect to the tube at all!