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Old 15th Mar 2017, 5:17 pm   #1
Radio Tech
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Default Portadyne Model Number

Hi Folks

Just got hold of this very old set, trouble is I cant find a model number on it so with the pictures I have taken of it so far is there someone who could identify it for me please, then I can get hold of the circuit diagram and service info.

Best wishes

Ken
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Old 15th Mar 2017, 9:51 pm   #2
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Default Re: Portadyne Model Number

Quite a puzzle, this one. I'd be fairly confident that it dates from 1935-40, and I have a Trader publication which gives basic information including valve complement for the models made by most manufacturers, including Portadyne, between those years, but all the AC/DC Portadynes listed specify valve rectifiers. I'm thinking that the dropper resistor at a rakish angle may not to be original, and that the set may have undergone considerable modification in the power supply section, possibly even from being AC only. Then again I can't completely rule out it dating from the early war years, when manufacturers were more likely to introduce circuit variants to make use of whatever parts they could get.

Valve numbers might be something to go on, are they all legible? I think I'm seeing a TX21 on the far right, a type that was used in a few AC/DC Portadynes: the Sept. 1937 U58, the Aug. 1938 TU38 and the three-valve Aug. 1939 U39. They're the only ones, though, and all are listed as using a 1D5 rectifier.

Paul

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Old 16th Mar 2017, 3:14 am   #3
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Default Re: Portadyne Model Number

Is that a 6P25 on the right? if so it may be an interloper, far left looks like -D21 to me ?
PM speaker so pre war is just possible.
The station names on the dial may give a date if you can read them.
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Old 16th Mar 2017, 3:36 am   #4
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Default Re: Portadyne Model Number

Looks very much like a late 30's model to me, I'd love to get my hands on that cabinet, it would respond very well to being refurbished.
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Old 16th Mar 2017, 9:55 am   #5
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Default Re: Portadyne Model Number

Hello Paul and everyone

The valves I took out are TX21, VP138, DDT13, PP35. the valve rectifier was missing. If you have the basic trader sheet Paul I would be very grateful. I have done a search for equivalents of the valves but cant find what would suite, at the moment I am trying to sort the underneath out, its in a bit of a mess.

Best wishes

Ken
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Old 16th Mar 2017, 11:11 am   #6
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Default Re: Portadyne Model Number

Hello Ken,

Those are pretty close to the specified valves in the booklet for the two four-valve AC/DC models there - the "VP138" will be a VP13B - so it may well be you have a U58 or TU38, with its 1D5 replaced by the metal rectifier. Maybe someone here will know one or other model and be able to confirm the identity or eliminate it as a candidate. As far as I know neither had a Trader sheet, and I'm afraid I haven't any information beyond the basic entries in Receiver Specifications and Prices - valves, retail price, release date etc.. IF is 450kHz for both models.

Paul
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Old 16th Mar 2017, 1:18 pm   #7
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Default Re: Portadyne Model Number

http://www.radiomuseum.org/r/halcyon_u573.html


The Halcyon U573 uses a very similar valve lineup- data available up top


http://www.service-data.com/search.p...&search=Search
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Old 16th Mar 2017, 3:44 pm   #8
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Default Re: Portadyne Model Number

Many thanks Paul and Chris for that info, and thanks to everyone else for their input, I will press on and update all when a little more progress made.

Best wishes

Ken
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Old 19th Mar 2017, 7:52 pm   #9
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Default Re: Portadyne Model Number

Here is an update on the progress, I removed the metal rectifier and rewired the mains dropper, whilst underneath I replaced the smoothing cap with something more fitting and replaced a couple of other caps, one being a coupler to another valve and the other a tone corrector. The tuning capacitor had to be removed in order to not only clean it but to see what was wrong with the bearings at the rear, this all became apparent as the sprung loaded bearing holder was bent and the bearing was lacking of grease. so here are a some pictures of the progress, the cabinet also is undergoing treatment.

Best wishes

Ken
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Old 23rd Mar 2017, 12:23 pm   #10
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Default Re: Portadyne Model Number

Hi folks

Got some spare valves and a rectifier for this set and powered it up but hardly any HT, I done a rough estimate of the total voltage needed to heat the valves and it works out around 134 Volts current around 0.2 A so that should have left around 96 V being dropped via the mains dropper, I checked this and got 105 V, all voltages measured with an AVO. Its a great pity I can not find the correct circuit diagram for this set as at least I would know if the valve line up is correct. The former owner of this set had a metal rectifier in and linked the heater pins on the rectifier valve socket, do not know how he got away with this as the heater volts for this valve are 40 V.

So any help or idea of what is going on appreciated

Ken
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Old 23rd Mar 2017, 2:54 pm   #11
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Default Re: Portadyne Model Number

I wouldn't have thought 105V as opposed to 96V is worth worrying about.

You say there's hardly any HT, but don't give a figure. I'd say that either you have a rectifier fault, or something (leaky caps) is loading up the HT.
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Old 23rd Mar 2017, 4:45 pm   #12
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Default Re: Portadyne Model Number

Hi Graham

Sorry forgot to mention the HT volts, this is around 46 V but this is not much higher with the rest of the circuit disconnected from the cathode of the rectifier, which does give the impression the rectifier is at fault but looks ok on the valve tester. Quite a mysterious fault.

Best wishes

Ken
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Old 23rd Mar 2017, 4:57 pm   #13
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Default Re: Portadyne Model Number

What's the AC voltage measurement on the rectifier's anode?

Lawrence.
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Old 23rd Mar 2017, 7:26 pm   #14
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Default Re: Portadyne Model Number

Hi Lawrence

The AC Voltage on the anode is as near to 230V which is our mains here. I also wondered if the mains dropper had been changed at some stage but as it has a ceramic body I could not see this being the problem of low HT. Just hope a circuit for the set turns up somewhere, it would make life a bit easier.

Ken
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Old 23rd Mar 2017, 8:21 pm   #15
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Default Re: Portadyne Model Number

Have you checked the voltage on the rectifier's heater?

Substitute a semiconductor diode for the rectifier. If the HT comes up you have a rectifier problem. If not the problem is elsewhere.
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Old 23rd Mar 2017, 8:37 pm   #16
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Default Re: Portadyne Model Number

What rectifier is fitted?

Lawrence.
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Old 23rd Mar 2017, 10:28 pm   #17
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Default Re: Portadyne Model Number

For a quick test, remove any valve (the heaters are in series, so none of the others will get warm) and see what the HT measures then, with only any leaking capacitors drawing current. Switch off the power and see if any of them have been getting warm. (If you could get hold of a thermal imaging camera, you could see straight away ..... not that I'm encouraging reckless purchase of test gear )

If you still get low HT after eliminating capacitor leakage, then the rectifier must be faulty. You can use a 1N4007 with a 100 Ω, 3 W resistor in series as a first replacement. Adjust the resistor value up or down as required to get the HT within spec.
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Old 23rd Mar 2017, 10:35 pm   #18
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Default Re: Portadyne Model Number

Won't unplugging any valve rob the rectifier of its heater supply?
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Old 24th Mar 2017, 2:41 pm   #19
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Default Re: Portadyne Model Number

Hi Lawrence, the rectifier is a 1D5 which I am told was a pretty much standard rectifier for this type of set. I will try and substitute the rectifier but of course would have to put a temporary w/w resistor in to substitute for the heater of the valve rectifier.

Regards

Ken
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Old 24th Mar 2017, 2:45 pm   #20
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Default Re: Portadyne Model Number

Quote:
Originally Posted by Radio Tech View Post
I will try and substitute the rectifier but of course would have to put a temporary w/w resistor in to substitute for the heater of the valve rectifier.

Regards

Ken
No need to do that if you're just checking the HT voltage. Not having the heaters powered will mean that the valves can't draw any current and won't pull the HT voltage down if say a screen grid capacitor is electrically leaking or the O/P valve is incorrectly biased.
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