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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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26th Mar 2017, 10:25 pm | #1 |
Octode
Join Date: Jan 2014
Location: Oban, Scotland, UK.
Posts: 1,129
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Hacker Helmsman transistor anomaly?
My recent Hacker purchase is undergoing a thorough check out and when checking the IF for potential AF117 tin whisker problems I discovered there are NO AF117's in there
The circuit consists of BF194B, BF195C and BF195D respectively for T2, T3 and T4 (which, according to datasheets are all NPN as opposed to the AF117 PNP). It would seem that the manufacturers redesigned this part of the radio at some time but the service sheet makes no mention of this (certainly not the copy I have). Has anyone got any information on this 'upgrade'? |
26th Mar 2017, 10:47 pm | #2 |
Nonode
Join Date: Jan 2008
Location: Milton Keynes, Bucks. UK.
Posts: 2,552
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Re: Hacker Helmsan transistor anomaly?
Sometimes these have been replaced by a previous owner as I believe, they can work in place of AF117's
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26th Mar 2017, 10:55 pm | #3 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,970
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Re: Hacker Helmsan transistor anomaly?
I think late production models had completely different circuitry with NPN Si replacing the AF117s. This would normally be a good thing, but unfortunately Hacker decided to use the dreaded Lockfit series which are becoming almost as troublesome as the AF11x types, though for different reasons.
There are several Hacker experts on the forum and one of them should be able to confirm this. Although the BF194/5s are HF transistors, I've found they can be replaced with jellybean BC548/2N3904 types if necessary, though the leadout is different so a bit of wire bending is necessary. If you actually need to buy replacements, or prefer to use specialist RF transistors, some cheap Chinese MPSH10s should be fine - these even have the correct leadout. |
26th Mar 2017, 10:57 pm | #4 |
Dekatron
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 9,433
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Re: Hacker Helmsan transistor anomaly?
From this thread post 40 http://www.vintage-radio.net/forum/s...=130015&page=2
It appears you have the later IF board T503, if so you may find a circuit of it on the later RP25 or later RP35. Frank |
27th Mar 2017, 12:08 am | #5 |
Octode
Join Date: Jan 2014
Location: Oban, Scotland, UK.
Posts: 1,129
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Re: Hacker Helmsan transistor anomaly?
Camtechman - the pcb seems designed specifically for these NPN transistors as the AF117 has the 'screen' wire that isn't accommodated on this board.
Paul - any problems and the devices will be replaced but currently all is working (fingers crossed) but given their obvious 'jellybean' status this makes the task very much simpler than the difficulties experienced by AF117 owners. Something to be appreciative for in any respect. Nuvistor - thanks for the pointer. Can anyone post a schematic for the IF board (only) so I can update my Hacker Helmsman download service sheet? |
27th Mar 2017, 2:38 pm | #6 |
Dekatron
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 9,643
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Re: Hacker Helmsman transistor anomaly?
IF board T503 is covered by the RP25B: http://www.service-data.com/section....overeign-mk-ii
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27th Mar 2017, 5:58 pm | #7 |
Octode
Join Date: Jan 2014
Location: Oban, Scotland, UK.
Posts: 1,129
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Re: Hacker Helmsman transistor anomaly?
Whilst I have no particular issue with paying again for another service sheet I feel that occasions such as this indicate that the data provided is misleading - will this be the 'only' additional sheet I require?
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27th Mar 2017, 6:32 pm | #8 |
Moderator
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Location: Ipswich, Suffolk, IP4, UK.
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Re: Hacker Helmsman transistor anomaly?
Why not buy the DVD?
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27th Mar 2017, 8:26 pm | #9 |
Dekatron
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 9,643
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Re: Hacker Helmsman transistor anomaly?
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28th Mar 2017, 9:34 am | #10 |
Dekatron
Join Date: Jun 2013
Location: East Sussex, UK.
Posts: 3,327
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Re: Hacker Helmsman transistor anomaly?
Don't think you can blame the data sheet as it will have been produced from makers data published before the later mods were implemented. It's not really possible to backtrack every mod that makers do and they often make changes for ease of production that are never noted.
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