Good morning Everybody,....

Being a new hand at this, I apologise in advance if I have made any errors in my post.

I was recently given a Pacemaker Valve radio (i have pictures if needed, all serial numbers and stickers still present) by a lady intending to bin it as it supposedly was not working. My first thought was to gut the internals and turn in into a speaker system for a garage radio.

On closer inspection I found that 2 of the 6 valves were in the wrong location and 3 were not seated correctly.
Checking over the rest of the circuit and application to the power bought everything back to life/light.... Yay,... a win for the little guy.

Looking to respect it's history and keep it as original state, but, as there is no discernible radio station through it, use it as an AMP for my 6 year old son's electric guitar using the "PICK UP" port on the back.

Any dating/age info would be cool to go with it for him

Bringing me to the questions that I have.

1. I would like to put a back on it so as little fingers do not pry and fry,.... will I affect the ambient heat / performance / safety etc? if I place a backing on it,.... I understand vent holes would be required.

2. Can the the valves be "upgraded" as such? to enhance performance/output, ie volume and tone. (this model has 4 dials.. tone, volume, tune and then a dial switch for GRAM or RADIO. )

3. Do the valves have a shelf/performance life and need replacement every so often?

4. What effect does incorrect valves have? I found one valve port had a circuit diagram requirement of an EB81 but in checking it, it had an EBF80 in it.

Again,.. apologies everybody if this is long winded or in breach of rules,... I have done my best to GOOGLE and TUBE the answers for myself, but not had any luck at all.

Many thanks for the help all.

Are you sure of EB81? Not listed. EBF81 (6AD6) perhaps? That is pin interchangeable but not the same. Its a medium cut of RF Pentode; EBF80 (6N8) is is a remote cut off RF AF Pentode.

They will not perform the same in radio mode. It is normally the components around the valve that are the problem. They will over a number of years of constant use loose emission, but I have put 80 year old ones back into service or left them in service.

Marc

Hi Ray,

To answer one of your questions Pacemaker radios were made by Collier & Beale of Wellington.

Going by the valve types you have mentioned suggests it could be late 50's or early 60's. This estimation of date is based on the 9 pin valves you mentioned. Unlike Australia, New Zealand radios prior to the mid 50's generally used 8 pin miniature Rimlock valves. Such valves are rarely seen here.

The valve type EB81 doesn't ring a bell. Are you sure it's not a EF81? Generally New Zealand radios used European designations for valve types. In Australia a EBF80 is known as a 6N8 & EF81 a 6BH5.

It is good that you want to keep this radio going & some photos would be would be most welcome. You can send the photos to Brad, the administrator, who will upload them to your post.

Thanks guys,....

Have emailed Brad some photo's to go with it also.

I could be wrong in the tube labels in that I hadn't noted them down, but had stumbled on this forum trying to find out info on them in general.

Any help or info on the condition of the capacitors and such would be appreciated,... in one of the photo's there is a picture of a 'grey' bar, that is slowly loosing its grey coating and exposing a fine wire winding,... again,... any info and guidance would be awesome.

In speaking to another person yesterday who remembered exactly the same model as a child,... yes Mono, a NZ made receiver, the labelling on the front panel are radio station names, not band indicators.

In plugging the guitar into it last night,.. I detected the cracked 'hum' from the speaker and from what I have read so far, it indicates towards capacitors beginning to fail.

Photos uploaded to Post 4.

Yes, it is a classic Kiwi radio from around the 1960 mark.

Don't want to be a bother, but could you take a close up snap of the label showing the valve positions. That would be a great help.

In plugging the guitar into it last night,..

It's never a good idea to power up old equipment that hasn't been used for years without first carrying out a thorough inspection. The danger is that faulty components, especially electrolytic capacitors, and shorts caused by perished insulation, among other problems, can cause irreparable damage to parts now in the 'unobtanium' category.

We can see evidence of component burning already.

If you do put a back on it, make sure there are plenty of air holes drilled into it.

I'd be replacing those waxed Ducon capacitors immediately. The wirewound resistor doesn't look too good either.

Can you please get a close-up of the dial, so we can read the stations marked upon it? Also the valve label as MonochromeTV asked.

Even though it's a NZ set, it has Australian parts and even a ARTS&P label.

NZ had their own ARTS&P decals which had very similar wording to the Oz ones. The major difference was on the 5th and 6th lines which referred to the Dominion Of New Zealand.

From a fading memory, I think NZ kept using this system for a number of years after Oz abandoned it.

The tuning unit appears to be a ferrite slug type unit.

As you mentioned, it has a few Australian parts such as the Ducon paper caps, the speaker looks like a typical Rola unit and the IFs are minature Philips.

Cheers, Graham...

One thing is for sure with that one. There needs to be a serious look at the socket, as there will be carbon tracking. I would suggest that there has been some serious heat been put into that resistor before it probably went open..... Caused by what?

I am another that says frequently; If its new to you, an unknown or has bee stored for ages: Plugging it in to see if it works, is not step one.

I fix: I see the damage.

Marc

Good morning all.

Thanks heaps for all the info everyone

Will endeavour to get the photos tonight on my return from work.

And also clarify the wrong tube that is in the wrong socket

Just to relax a few nerves, I did run a PAT test on it before I plugged it in, through an RCD plug. A standard process I have had with new and old parts on my work bench, but as it is just a normal habit for me, I didn't think to mention anything of it. When my son will be using it, it will be via a 10 amp protection plug between the main socket and the radio.

The standard electrical side of things I am ok with, but the older radio/circuitry as here will be a new branch on the learning tree.

Are parts still possible to get hold of, costs? or is it going to be something better left as a 'conversation piece' so to speak, there is no audible station pick up in the tuner.

What sort of lengths have you guys gone to before abandonment to the 'spares pile.

cheers
Ray

Most, but not all, parts are readily available, your radio is a definite restoration prospect.

But you should NEVER EVER power up an old radio without a full check and replacing paper caps. It's an exercise in futility. There is a procedure to be followed (mentioned many times on this forum) for re-forming the electrolytics. An RCD or breaker will not save you from damaging mains transformers (expensive to get re-wound), valves (available but often expensive) and other parts that just make the repair more difficult and expensive. Electrolytics can and do explode, spraying the internals with corrosive substances. Or they short out, taking out the mains transformer, rectifier valve et al. You get my point I'm sure.

That damaged wirewound resiistor is evidence that the set has been running with (probably) a leaky paper cap mis-biassing the output valve and drawing excessive current, damaging everything else in its path......

Once fixed. the radio will be safe to use with no need for external protective measures.

Thanks Ian, will try to locate someone here in NZ who will have them.
I wanted to put a backing on it purely for safety as with having a 6 and 3 year old around it, I didn't want to risk the possibility of little inquisitive fingers prying and frying either on the electrics or a hot valve.

As a restored unit, with capacitors replaced etc, what sort of dollar value would it then hold?

Monochrome, Brad has the pictures to post.
In the picture with the from channel glass, where the indicator bar is, it actually picked up our Trackside station, so further restoration as indicated by Ian is definitely in the forward plan.

The picture of the valve layout,... the first valve on the right, is an EZ81, but it currently has an EZ80 in that location, (it was the valve that I had mentioned in my initial post that was out of sequence, I had just got my alpha coding mixed up.) how this effects everything, I don't know.

Supplementary photos uploaded to Post 13.

An RCD and an insulation test is not your saviour. I will insulation test all HV transformer windings and especially between filament windings running a rectifier: But!

Most of the impending damage will be caused on the HV secondary side from failed components and bad wiring; it is therefore, folly to just do these tests and think you can power it. Also many Valve PA amps are dangerous. I have one that is capable of 300VDC, after the filters, at near 500mA, well within the range that can kill and I have doubts that an RCD would trip.

Once it has been established that the LV windings are OK & not shorted by deteriorated wire etc. You then have to disconnect the rectifier. E.g If its a filament valve like #80 / 5Y3 you remove it. You can use an ohm meter to establish if the primary, filament winding (if it has one) & HV secondary are not open. Then and only then, if the wiring is safe both sides of the transformer, may you power it to see if it is OK.

Removing or disabling the rectifier is essential to ensure that no DC "B" Voltage is developed; this allows voltage measurements on the transformer, to help establish viability of repair. Never measure across the HV winding (eg pin 4 to pin 6 of a 5Y3) with a meter that cannot withstand at minimum one KV. Many circuit diagrams have no voltages on them and if it happens to have a 400-0-400 VAC HV secondary, many modern voltmeter / multi-meters cannot handle that voltage, RF or, the DC voltages within. You may need an Industrial type meter?

"Caveat Actor" applies when working on, especially, mains sets.

Marc