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Old 24th May 2017, 10:42 pm   #1
ricksteptoe
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Default Chapman FM1005 tuner

Evening all,
I have just dragged this tuner out of the shed, where it has been living since moving house. I was given it some years ago, but had no need for it at the time.
On inspection it has a high proportion of AF series transistors (9), and will require major surgery to release the boards to replace them. I have never come across the make before, so don't know if it is worth the effort. Can anyone advise if it is :-
a) any good, and
b) what would be suitable replacements for the 3 x AF115, 4 x AF116, and 2 x AF117 transistors.

I am not skilled with "4-legged fuses" and tracing pcbs, main interest is valve gear, whith which I am reasonably competent.

Any thoughts would be gratefully received.

Rick.
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Old 24th May 2017, 11:32 pm   #2
paulsherwin
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Default Re: Chapman FM1005 tuner

It's an early 60s transistorised FM tuner, which you probably knew already. I don't think it's particularly sought after in the hifi world but is an interesting historical item and worth saving.

There are many threads on the forum about replacing AF11x transistors if you search, but the gist is:

1. The AF115, 6 and 7 are all the same transistor.
2. You can repair shorted AF11xs by zapping them, at least temporarily.
3. The AF12x series is a direct replacement for the AF11x.
4. Most germanium HF transistors will work as replacements if the Ft is high enough, including cheap and easily available USSR types.
5. Jellybean silicon PNP transistors like the 2N3906 or BC558 will often work.

If you have no real interest in this era of technology it may be better to pass it on, though it should be a fairly easy restoration and a good first project for someone new to transistor designs.
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Old 26th May 2017, 1:21 am   #3
Synchrodyne
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Default Re: Chapman FM1005 tuner

The Chapman FM 1005 FM/AM tuner was introduced in mid-1963, along with the FM-only FM1000, as its initial step into solid-state circuitry. They could be seen as being replacements for the valved FM95 and FM91 respectively. So the FM1005 was pitched well below the performance level of say the SB6S/FM model. The small-signal germanium transistors of the time probably would not easily have allowed that level of performance anyway.

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The FM1005 went through FM1005A, FM1005A/B and FM1005A/B(D) iterations until it was first supplemented and then superseded by the (probably very similar) FM2005 circa 1970. Derritron/Chapman withdrew from the tuner market soon after that.

Cheers,
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Old 26th May 2017, 6:38 pm   #4
ricksteptoe
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Default Re: Chapman FM1005 tuner

Thanks for all the info guys, I've ordered 10 AF126 which should arrive in the next few days. I found another AF116 hiding behind a coil so will need the extra one! This should keep me quiet for some time as every pcb will have to be removed due to the method of construction, and the wavechange switch will also have to be dis-assembled to gain access. It makes doing the condenser block on a mid 30's HMV look easy.

Regards,

Rick.
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Old 27th May 2017, 12:58 am   #5
Synchrodyne
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Default Re: Chapman FM1005 tuner

Here is the Hi-Fi News review of the FM1000:

HFN 196404 p.911,913.pdf

As I understand it, the FM section of the FM1005 was essentially the same as the FM1000.

Generally, Chapman tuners had a good reputation. Apparently Leak used to suggest Chapman to customers who wanted FM-AM rather than FM-only tuners, as it offered only the latter type itself.

Cheers,
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