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Old 11th Oct 2018, 3:15 pm   #1
vampyretim
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Default Hmv 2346 af115

Hi,

I'm repairing an HMV Radiogram. I've repaired the amplifier side and am now moving onto the radio. Neither F.M or A.M work. I'm not getting any emitter voltages across VT4 or VT5 so have taken out the transistors to test and I'm getting identical resistance in both directions of the junctions. The transistors are those horrible AF115's/AF116's. What do you guys replace these with?

Many thanks.
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Old 11th Oct 2018, 3:18 pm   #2
Boater Sam
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Default Re: Hmv 2346 af115

Just about any germanium signal transistor. If you search here for AF117 replacements you will find pages of posts about substitutes for the Mullard AF11x series.
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Old 11th Oct 2018, 4:53 pm   #3
Herald1360
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Default Re: Hmv 2346 af115

For the VHF front end and IF, you need a passable RF transistor, not just any old Ge PNP.

AF124/5/6/7 are electrically though not physically identical but quite expensive now. Russian GT322B are also good electrically and somewhat cheaper, though the days of packs of 100 for 20 are no more......
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Old 12th Oct 2018, 2:40 pm   #4
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Default Re: Hmv 2346 af115

Thanks guys.
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Old 12th Oct 2018, 4:49 pm   #5
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Default Re: Hmv 2346 af115

I have used AFZ12 amongst others with good results. The mixer/oscillator is usually the most fussy. Many RF transistors will work providing they are PNP with a good frequency rating, even some silicon transistors often work.
But why use silicon and risk having to adjust the bias when there is a lot of germanium still around?
What have you got in stock? Solder some longer leads onto the pcb and hook up a few odd ones to see if they work.
Sam.
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Old 12th Oct 2018, 5:14 pm   #6
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Default Re: Hmv 2346 af115

Search the forum, there are dozens of threads about this.

Replacement is usually straightforward with Ge and often with Si too. You need an Ft of 120MHz for the mixer and 20MHz for the IF amps, though higher ratings will obviously be OK too.
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Old 12th Oct 2018, 5:29 pm   #7
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Default Re: Hmv 2346 af115

It seems the FM front end uses 2 BF160 transistors, these may be OK.
If you check out the service data available from up top then it gives the equivalent AF12x transistors. VT3 & 4 AF125, VT5 & 6 AF126.

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