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Old 8th Mar 2018, 12:32 pm   #1
Hunts smoothing bomb
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Default Hacker Sovereign

Hi all,

I've had a Hacker Sovereign on the bench now for a while as I'm going through it for a friend who would like it restored to working order as it has sentimental value.

When I got the set it was completely dead, not even the amplifier was working.
I found that the electrolytic caps on the amplifier board were leaky or short circuit, replacing these restored the amplifier to working condition.

The usual problems with tin whiskers in the AF117's was the issue with the I.F strip for the MW/LW bands and I have got this now working also by deploying the charged capacitor "zapping" method,

The FM side is still dead and measuring the voltage to the FM I.F. strip shows that it is low just like the MW/LW I.F. was.

I have tested two out of the 4 AF114's so far from this FM I.F. strip on my Atlas Peak component Analyser and it comes up saying that they are a "Bi-Colour LED!" When I tested the AF117's it told me that the duff ones were either "short circuit" or "diode or diode junctions"

So I can only presume that this means that the transistors are duffers right?

Cheers
Lee
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Old 8th Mar 2018, 12:44 pm   #2
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Default Re: Hacker Sovreign

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Originally Posted by Hunts smoothing bomb View Post
I have tested two out of the 4 AF114's so far from this FM I.F. strip on my Atlas Peak component Analyser and it comes up saying that they are a "Bi-Colour LED!" When I tested the AF117's it told me that the duff ones were either "short circuit" or "diode or diode junctions"

So I can only presume that this means that the transistors are duffers right?

Cheers
Lee
That's certainly been my experience. If a Peak Atlas tester wrongly identifies a device, the device is duff.
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Old 8th Mar 2018, 2:13 pm   #3
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Default Re: Hacker Sovreign

Not so in my experience. The Peak Atlas often does this with germanium transistors.

For the RP18, I've never had to do anything other than "treat" the AF114s to restore full FM operation. I've lost count of the number I've done, but it'll easily be more than a dozen.

Obviously I can't say conclusively that yours aren't faulty, but statistically, it would be unlikely. Zap them and give it a go. You could even temporarily "tack" them on the rear of the PCB for testing to save a bit of time (emptying out those metal pillars is a bit of a pain).
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Old 13th Mar 2018, 8:30 am   #4
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Default Re: Hacker Sovreign

Hi all

I'm still plodding away with this set as time permits and I've replaced all the AF114's in the FM IF stage now with GET882's
Now, on paper I think these should work but FM is still dead. I haven't checked yet but I'm assuming that the FM IF frequency is around the normal 10.7Mhz and if so I was thinking that I could test the IF by feeding in a 1Khz modulated 10.7Mhz signal then this should give me audio at the loudspeaker, am I correct with that presumption? I have also ordered some AF178 transistors incase the fault is still down to incompatibility with the GET882 devices that I have fitted.

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Old 13th Mar 2018, 9:45 am   #5
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Default Re: Hacker Sovreign

Is that an AM modulation or FM? An AM one will get through if strong enough but the circuit is designed to reject AM.
Just feed a 10.7 MHz signal unmodulated if you haven’t got FM and measure the voltage across the AM supression cap, that’s the electrolytic across the FM discriminator.
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Old 13th Mar 2018, 10:03 am   #6
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Default Re: Hacker Sovreign

I would do a DC check of the AF114's that you removed with a DMM first and then treat them if required. Then try refitting them to see if the FM stage comes up.
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Old 13th Mar 2018, 10:27 am   #7
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Default Re: Hacker Sovreign

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Originally Posted by Hybrid tellies View Post
I would do a DC check of the AF114's that you removed with a DMM first and then treat them if required. Then try refitting them to see if the FM stage comes up.


Thanks Simon,


They've already been checked on a Peak Atlas component tester, two test ok and two test as Bi-colour LED's


I have tried the usual "blasting tricks on the AF 114's as I did on the AF117's in the AM IF stage but sadly has not worked.


Would somebody be able to tell me whether the GET882 should work as a substitute or not? (I have pretty much the correct circuit voltages now for the FM IF stage but still no audio)


Cheers
Lee
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Old 13th Mar 2018, 11:29 am   #8
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Default Re: Hacker Sovereign

I have had a couple of AF114’s fail in the Sovereign. No amount of zapping will bring them back. I replace with AF124 or GT322B. As far as the GET882 is concerned I wonder whether it is any good for FM as the transistor frequency is only 6MHz while the AF114 is 75MHz. Maybe someone who knows a lot more about transistor applications can confirm whether this is the case. I have a good stock of GT322B if you want to try them.

Good luck

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Old 13th Mar 2018, 11:33 am   #9
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Default Re: Hacker Sovereign

I doubt a GET882 will be good at 10.7 MHz. Its Ft is given as 6 MHz.

https://alltransistors.com/transisto...ansistor=35626
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Old 13th Mar 2018, 11:35 am   #10
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Default Re: Hacker Sovereign

Agreed, GET882s aren't up to the job in an FM set. You need something with an Ft of at least 20MHz for the IF stages and higher for the mixer/osc. You may find that a silicon transistor such as a BC558 or 2N3906 will work, at least to confirm the transistors are responsible for the fault.
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Old 13th Mar 2018, 12:01 pm   #11
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Default Re: Hacker Sovereign

Thanks chaps for the info,

I did not realise that the headroom on the 882's was 6Mhz, I have some AF178's coming that I will try, they were mentioned as an excellent substitute https://www.vintage-radio.net/forum/...1&postcount=15

Cheers
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Old 13th Mar 2018, 12:39 pm   #12
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Default Re: Hacker Sovereign

I would expect those to be fine.
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