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Old 22nd Nov 2020, 10:25 pm   #1
DecHughes
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Default Portadyne RG193 radiogram - no sound

Hi all,

I recently picked up a Portadyne RG193, it looks to be in good condition. The backlight in the tuner comes on when powered up and the turntable appears to function also. Unfortunately there is no sound from the speaker at all.

The seller told me that when he listed it the sound was not working. But when he brought it downstairs to get it ready for us to pick up the sound came back. He demonstrated it working for me. Unfortunately by the time we got it home the sound had gone again.

There is a very quiet sound from the turntable when a record is playing but not from the speaker. Nor is there any hum or crackle when the system is turned on.

I've open it up and had a look at the circuitry and there does not appear to be any obviously damaged components or loose connections. There is a crackle from the speaker if I flex the wires where they connect to one of the boards so I believe the speaker is working.

Would anyone be able to give any advice on how to get this working again?

I've never worked on a radio/record player before but have a basic knowledge of electronics. Any advice would be appreciated.

Thanks,
Declan
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Old 23rd Nov 2020, 10:50 am   #2
Edward Huggins
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Default Re: Portadyne RG193 radiogram - no sound

What you are hearing from the record is just "stylus chatter". This is a rather basic AM Mono unit, so it's not too complex. Do check the cartridge connections. Don't worry about the speaker, they rarely fail. You will need to meaure the voltage on the main DC rail at that large blue cap seen in photos #3 and 4. You should betting c.20V or more. I regret I don't have a circuit for this to be more accurate.
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Old 23rd Nov 2020, 12:47 pm   #3
DecHughes
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Default Re: Portadyne RG193 radiogram - no sound

Hi Edward,

Thanks for responding �� I'm in work right now but I'll check the cartridge connections and get a measurement of the voltage when I get home and let you know what it's coming in at.

Many thanks,
Declan
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Old 23rd Nov 2020, 1:41 pm   #4
John10b
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Default Re: Portadyne RG193 radiogram - no sound

In your post #1 you said the seller said it did work but then after moving it, the RG stopped working, if this is correct you may have a bad connection, so may I suggest, with the RG on, you try tapping around the chassis and interconnections, using an insulated probe, and taking great care, as you will have mains voltage going to chassis.
You could also try turning the various controls, I don’t have service information so I can’t be more precise, this can sometimes locate the problem.
John
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Old 23rd Nov 2020, 6:37 pm   #5
DecHughes
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Default Re: Portadyne RG193 radiogram - no sound

Quote:
Originally Posted by Edward Huggins View Post
What you are hearing from the record is just "stylus chatter". This is a rather basic AM Mono unit, so it's not too complex. Do check the cartridge connections. Don't worry about the speaker, they rarely fail. You will need to meaure the voltage on the main DC rail at that large blue cap seen in photos #3 and 4. You should betting c.20V or more. I regret I don't have a circuit for this to be more accurate.
I've checked the cartridge connections, one of them was a little loose but reseating it has made no difference.

I've measured the Voltage on the DC rail indicated in the attached image and have a 21v reading.

Quote:
Originally Posted by John10b View Post
In your post #1 you said the seller said it did work but then after moving it, the RG stopped working, if this is correct you may have a bad connection, so may I suggest, with the RG on, you try tapping around the chassis and interconnections, using an insulated probe, and taking great care, as you will have mains voltage going to chassis.
You could also try turning the various controls, I don’t have service information so I can’t be more precise, this can sometimes locate the problem.
John
Thanks for the tip, unfortunately I've already tried prodding and flexing connections and parts around the board with a wooden stick to no avail.
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Old 24th Nov 2020, 11:43 am   #6
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Default Re: Portadyne RG193 radiogram - no sound

It’s rather difficult to give you precise information without the service manual/circuit diagram, so it means further investigation, you could still have a bad/faulty or dry joint interconnection. Have you tried operating the various controls ?
John
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Old 24th Nov 2020, 11:48 am   #7
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Default Re: Portadyne RG193 radiogram - no sound

In the enhanced picture I’ve attached can you say what the various controls are ?
John
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Old 24th Nov 2020, 12:07 pm   #8
Edward Huggins
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Default Re: Portadyne RG193 radiogram - no sound

They will be for Tuning, Volume and Tone. It looks like the are push buttons for On/Off, Gram, MW and LW. This is a very simple radio with no FM or Stereo/Mono switching.
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Old 24th Nov 2020, 12:36 pm   #9
dave walsh
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Default Re: Portadyne RG193 radiogram - no sound

Looks like it's solid state Declan. Is that your electronics experience? Three basic controls and 4 pushbuttons as Edward observes, two to pre-set stations maybe. There doesn't seem to be a circuit to download in the very useful section provided by the site owner on here [top right on the front page]. It will be late sixties/early seventies product perhap It's not very easy to locate info on Portagram [also known as Dynaport] sets at all. I've got a very much earlier [valve] Radiogram [with a bakelite record deck] and a table top radio. I've not been able to find anything out about these. If you google "Radiomuseum Portadyne" it will bring up an online resource with [unfortunately] a not very comprehensive list. If you are not familiar with these items you might need to do a bit of reading around the subject initially. There will be help available as you progress I'm sure but be careful, vintage restoration is addictive! There is a very useful sticky about Radiograms at the top of this section written by Darren in 2008. It's very comprehensive and only out-dated by the fact that you couldn't give RG's away for decades-nobody wanted them! Now everyone does in the "Retro" age. [Take a look on auction sites].

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Old 24th Nov 2020, 5:57 pm   #10
John10b
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Default Re: Portadyne RG193 radiogram - no sound

Thank you Edward for confirming it has Push Buttons, I wasn’t sure. Try pressing these several times, they can cause problems.
John
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Old 29th Nov 2020, 1:13 pm   #11
DecHughes
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Default Re: Portadyne RG193 radiogram - no sound

So I've gone through all connections and cannot find any poor solder joints.

I've had a go at checking voltages with a multimeter. I've located the signal line into what I think is the amp and I am getting about 0.1V max AC reading with the volume knob turned all the way up.

Does this seem reasonable for a unit with a 20V DC powered amp?

I have also tried to trace the signal through the amp, it goes into the base pin of a transistor, but I cannot pick up any AC voltage on either of the other two transistor pins. I have taken the transistor out of circuit to check if it is functional and it appears to be working okay.

Does anyone have an idea why the AC would not be getting through the transistor?
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Old 29th Nov 2020, 7:35 pm   #12
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Default Re: Portadyne RG193 radiogram - no sound

Declan it’s rather difficult to guide you into fault finding on your RG without the circuit diagram. So any advice given should be treated as a general guide, and with added caution that mains voltage will be present.
With the RG on, and the volume control turned to max try touching the terminals, you should get a decent buzz if amp and psu are ok. Let us know how you get on.
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Old 29th Nov 2020, 11:06 pm   #13
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Default Re: Portadyne RG193 radiogram - no sound

I should have made clearer it’s the terminals of the volume control you touch.
John
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Old 3rd Dec 2020, 10:39 pm   #14
DecHughes
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Default Re: Portadyne RG193 radiogram - no sound

Hi John,

I have touched the volume control terminals and there was no sound from the speaker.

I think the issue is with the amp, I am working on a circuit diagram of the amp at the moment that I can share when it is done.

One thing I have noticed that is odd is that two of the metal encased transistors on the amp board get quite hot while the system is powered up, but the third stays cold. Could this third component be the issue?
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Old 4th Dec 2020, 12:12 pm   #15
John10b
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Default Re: Portadyne RG193 radiogram - no sound

Hi Declan
In your first post #1 you say you get a crackling from the speaker, so I’m assuming the LS ( only one LS ?) is ok.
I’m reluctant to say what could be wrong, I don’t want to just say something for the sake of it, so it really is a matter of fault finding, of course one or more ( depending on circuit configuration) of the transistors could be faulty. I haven’t noticed a fuse , is there one fitted ?
May I suggest you try and confirm the power supply- PSU - is ok, I know the transistors are getting hot so it may be the psu is ok, but try checking anyway.
I’m sorry I can’t be more definitive, it’s tricky without service manual ( circuit diagram).
John
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Old 4th Dec 2020, 12:17 pm   #16
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Default Re: Portadyne RG193 radiogram - no sound

Hi Declan , I forgot to say try removing the metal housing from the two transistors, this has worked in the past for transistors that go short circuit.
John
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Old 4th Dec 2020, 2:44 pm   #17
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Default Re: Portadyne RG193 radiogram - no sound

That looks like a standard Philips/Mullard module and the transistors will get hot without the heatsink. This maybe the same as the Unilex modules.
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