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Old 27th Feb 2018, 10:14 pm   #1
poppydog
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Default Akkord Pinguin U60

I have an Akkord Pinguin U60 transistor radio that I have an issue with:

https://www.radiomuseum.org/r/akkord..._u60_u_60.html

The problem I am having is on all wave bands all I am getting is a hiss. Its currently drawing 27ma, the voltages across the transistors are almost as per the sheet. I am using the voltages and current specifications from the US version of the radio schematic as the version on the radio museum link above doesn't specify them. I can't imagine there being much difference between the two radios? I have injected a tone with my newly acquired signal generator across the speaker and to the base and emitter of all of the transistors, up to and including the 1st FM IF Amp -AM conv., the tone is being heard across them all. This is quite a complex radio for the likes of me, however I would like to get this one going, so some pointers in the right direction would be appreciated.

Regards
Poppydog
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Old 28th Feb 2018, 1:40 pm   #2
GeoffK
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Default Re: Akkord Pinguin U60

Hello Poppydog,

The switches should be checked first as these are quite complex and a fault in any one could stop the radio working, the ones common to all bands should be looked at as no bands are working.

Forget about the FM stage for now, on AM it is disconnected. Assuming AM IF is 470KHz

Take another working radio and tune it to a quiet spot on the MW band. Place the output of the signal generator near it and sweep the signal generator control past the 470KHz on the scale until you hear the tone in the radio, peak it so this is the 470KHz setting (band 4) on the signal generator. Turn the output level control to the minimum setting.

With a 0.01uF capacitor on the signal generator output probe and the internal MOD switched on and screen attached to the chassis, touch the probe against the cathode end (tap of L20) of the AM detector K5/2. Adjust the output for a minimum tone level with the volume control of the Akkord set to around half way, turn volume up and down to hear change in volume level, showing that the audio stage is working.

With the output of the signal generator set the same, and make sure it is the minimum that it can still be heard, put the capacitor probe on either C50 or C51 the base of second IF T4. The audio tone should get louder as T4 amplifies it.

Repeat by touching the probe to first IF T3 base C40, again the audio tone should get louder.

Finely put the probe against C22 and the audio should get slightly louder if T2 is amplifying.

If there is no amplification at any stage the transistor could be suspect or any of the components surround it. Other things to check is visually as it is all hand wired for any broken components or connections, and resistance checks of the various coils.

T2 the AM oscillator and FM first IF amplifier could be where the fault is if it is not oscillating on AM, but any of the small capacitors within the coil cans could be faulty, though these don’t often fail.

Make sure if you are supplying with a power supply that the current limit isn’t set to low, 500mA or so. Limiting the current to much can stop things working.
But the most likely culprit is one of the switch connections.
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Last edited by GeoffK; 28th Feb 2018 at 1:52 pm.
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Old 28th Feb 2018, 2:37 pm   #3
poppydog
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Default Re: Akkord Pinguin U60

Thanks for taking the time to reply Geoff. I will have a look later and also try to put some pics on, not looking forward to those switches
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Old 1st Mar 2018, 10:16 pm   #4
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Default Re: Akkord Pinguin U60

Hello Geoff, sorry for the delay but its been snowing .

With regards to the switches its been nigh-on impossible to work out what does what, the schematics help a bit but its such a mish mash. However I will have another look. I have never seen so many components crammed in and sleeved making it impossible to see what goes where.

I have put a tone into K5/2 which was a pain to locate however if you had said D2 a OA160 it would have been better for me . Got a good loud tone.

I have put a tone into C50 IF-T4 and it is loud and clear. T3, I am not getting anything across C40/base, when I did this the other day I was getting a tone?? T2, I am getting a tone across C22, I am also getting a tone just putting my probe near T2.

Would I get a tone across T2 if T3 was not good?

I have never come across one of those black glass transistors that has been faulty. Its an AF105 and I need to be sure its faulty before I attempt to remove it as its crammed in there with everything else.

Current limit is fine.

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Old 2nd Mar 2018, 1:30 pm   #5
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Default Re: Akkord Pinguin U60

If you take voltage readings of the transistors and get nearly battery voltage of minus 6 Volts at the collectors of T2, T3, T4 and a volt drop of around 300mV between the base and emitters it is reasonable to say the transistors are working, (along with a foward/reverse ‘diode’ junction check with power turned off) as far as their DC condition is concerned. If you are getting a tone through T2 then it must also be amplified by T3 if you can hear the audio tone. The audio tone from the base of T3 should be louder than the audio tone at T4 and the detector diode. But you need to find out if T2 is oscillating on the AM band and that could be down to one of the switches in its base circuit not closing or the switch associated with L4 the oscillator coil. C21 C22 C23 are the coupling capacitors around the oscillator stage. The switches although complex can be broken down into stages one switch bank at a time and comparing with the schematic, print off a copy and mark each switch off as it is checked, this can be done with the power off and a resistance check either at the switch contacts or where the switch is meant to connect. For example the LW (tag 58,59) and MW (tag 51,52) aerial coil (L8,L6 secondary) switch, in turn, go to C21 and the switch to L4 should then close (tag 20, 21 on my schematic). In the schematic the switches are shown set to FM, the MW LW ferrite aerial is open circuit and L4 the oscillator coil is shorted by tags 21,22. T2 then acts as FM first FM IF amplifier via switch tags 17,18 in T2 collector.
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Old 2nd Mar 2018, 10:51 pm   #6
poppydog
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Default Re: Akkord Pinguin U60

Hello Geoff

I have already taken transistor voltages, however I will take them again and also I want to try putting a tone across the base of T3 again, I will do this and more tomorrow. Just one more thing - In my first post I mentioned that I am getting a hiss on all wave bands, I am also getting that same hiss when switched to PU, (I take it this is for the din output) don't know whether this makes any difference as to where to look.

Some pics for you...

Regards
Poppydog
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Old 3rd Mar 2018, 6:58 pm   #7
GeoffK
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Default Re: Akkord Pinguin U60

An external audio amplifier, it could be the audio stage of another radio, connected directly to the detector diode output would show if there is anything coming out of the AM bands. Likewise a low level audio input directly across the volume control would show the internal audio stage is working. The only bit in-between is the switching from AM to FM and the switching to the external audio input via the din socket and other sockets, probably 4 mm for a record player or tape recorder. If the fault is not here then each stage back from here would have to be checked, the other switches being the main area to check. Being built without a printed circuit there could be poor or broken solder joints.
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