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Old 28th Sep 2017, 5:51 pm   #1
Dave Moll
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Default "Genie" telephone

I have recently acquired a "Genie" telephone (the 'phone that looks like Aladdin's lamp) with a rather odd fault, in that it rings on an incoming call, but fails to make a loop. Although the ringing stops when the handset is lifted, the calling telephone continues to receive ringing tone, and the ringing resumes if the handset is replaced.

Because it fails to make a loop, then handset is dead when lifted, whether or not there is an incoming call. The problem doesn't appear to be with the gravity switch, which has two pairs of contacts, both of which are closed on-hook and open off-hook.

Any thoughts on where to look next would be appreciated.
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Old 28th Sep 2017, 6:45 pm   #2
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Default Re: "Genie" telephone

I assume the 2 contacts on the gravity switch are for line switching and anti-tinkle.

The latter will short-circuit the internal bell/ringer which explains why it stops ringing when you lift the handset. But it will not complete a DC loop across the line, so that's why it doesn't cause the exchange to remove the ringing voltage, etc.

First thing to check is the line cord. If the pin 2 wire (red) is open-circuit then the phone will behave like that as you only need pin 3 (blue) and pin 5 (white) for the ringer and anti-tinkle switch.

If that's good, then you will have to trace through all the wiring in the telephone to see just how the DC loop is completed and why it isn't working in this case.
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Old 28th Sep 2017, 9:25 pm   #3
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Default Re: "Genie" telephone

Thanks. I've checked all four line cord wires and confirmed continuity on each through to the connector on the circuit board; also confirmed the presence of 50VDC between red and white at that connector when plugged in. It looks, therefore, as though I'm faced with following the tracks as you suggest.

I'll report back with any progress.
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Old 29th Sep 2017, 8:40 am   #4
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Default Re: "Genie" telephone

Our very first 'inphone' when I lived with the parents. It was expensive. Ours was in the peach colour (still got it) and stamped 'Made by AP Besson' at the bottom. It was one of those things that Mum 'just had to have'.

Being an earlier one there was no redial, just a couple of blank buttons.
The place where the redial button was later installed still worked if you were trying an engaged line, but it forgot the number if you went back to it a few minutes later.
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Old 30th Sep 2017, 7:26 am   #5
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Default Re: "Genie" telephone

Hi, I do not have mine in the house, so I can not test it , but mine had an odd configuration on the RJ jack in the phone. I can not remember if it had 2 wires going in, and 2 to the ringer, or r wires + 1 to the ringer. Mine was made in Norway according to paper sticker under the phone.

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Old 6th Oct 2017, 6:48 am   #6
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Default Re: "Genie" telephone

I did think to have a go at tracing out the circuit, as there's not too much in the way of discrete components outside the three chips. The problem I've encountered, though, is that I can only find datasheets for two of the chips. The one I can't find is labelled:

MEDL 8721
ZMA522PO

Presumably, this is a custom chip. Would that "PO" at the end signify "Post Office" by any chance?
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Old 6th Oct 2017, 7:01 am   #7
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Default Re: "Genie" telephone

Not sure about the PO but MEDL is the manufacturer (Marconi? Now Dynex?), and 8721 the date code so presumbaly its part number is the ZMA... bit.
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Old 6th Oct 2017, 10:48 am   #8
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Default Re: "Genie" telephone

I came across an MEDL chip in a Tribune telephone andalso couldn't find data on it. But as the other 2 ICs were Texas Instruments (and I have the appropriate databook on the kitchen shelf...) I quickly found those were the speech circuit ('hybrid', replaces the induction coil) and the ringer. Since the unknown IC linked to the keypad, I deduced it ws the dialer.
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Old 6th Oct 2017, 12:21 pm   #9
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Default Re: "Genie" telephone

Quote:
Originally Posted by Nickthedentist View Post
... presumably its part number is the ZMA... bit.
Yes, I tried a search on that as well and came up with nothing relevant.
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Old 6th Oct 2017, 12:24 pm   #10
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Default Re: "Genie" telephone

Quote:
Originally Posted by TonyDuell View Post
Since the unknown IC linked to the keypad, I deduced it was the dialer.
I'm in the library at the moment, so I'll check when I get home, but I think one of the other chips was the dialler.
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Old 6th Oct 2017, 6:46 pm   #11
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Default Re: "Genie" telephone

Can you post the numbers of the other 2 ICs so we can see what functions they perform, please
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Old 7th Oct 2017, 5:50 am   #12
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Default Re: "Genie" telephone

MC34017 and TEA1061. As I say, I have data sheets for both of these. The latter is described as "versatile telephone transmission circuits with dialler interface".
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Old 7th Oct 2017, 6:50 am   #13
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Default Re: "Genie" telephone

Quote:
Originally Posted by Nickthedentist View Post
Not sure about the PO but MEDL is the manufacturer (Marconi? Now Dynex?), and 8721 the date code so presumbaly its part number is the ZMA... bit.
MEDL was the unfortunate acronym for "Marconi Electronic Devices Ltd"

I do wonder sometimes about the mindset of those who come up with company names.
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Old 7th Oct 2017, 9:22 am   #14
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Default Re: "Genie" telephone

Ah, thanks Chris.

And no, I don't think the "PO" refers to Post Office, as everything was well and truly BT'd by 1987.
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Old 7th Oct 2017, 11:56 am   #15
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Default Re: "Genie" telephone

The TEA1061 is the speech circuit (the replacement for the induction coil), the comment about the 'dialer interface' means you can link a dialer chip to it (it has a pin to inject the DTMF signal). The MC34017 is a ringer. So that means that (as in the Tribune I was working on) the MEDL IC is the dialer.

Is there a discrete transistor circuit acting as a line switch hung off the dialer chip? If the telephone supports pulse dialing then that is likely. If that's failed the telephone won't loop the line.
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Old 7th Oct 2017, 5:58 pm   #16
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Default Re: "Genie" telephone

Ah, now I understand, "dialler interface" means that it interfaces with the dialler rather than being the dialler itself. I'll check out the wiring round the MEDL chip, but if this means the chip's blown, it doesn't sound hopeful.

By the way, I had meant to say that I had identtified the MC34017 as the tone ringer. My previous reply was typed in a hurry, as I had to head off early this morning.
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Old 14th Oct 2017, 5:19 pm   #17
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Default Re: "Genie" telephone

I have one of these. I took it apart in order to take some components, and found this forum/thread when I was searching for MDEL 8721 ZMA 522.
Dave, if you would like it [the whole phone or the chip if I can get it off]? I'd just need postage.
-John
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Old 14th Oct 2017, 7:12 pm   #18
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Default Re: "Genie" telephone

PM sent.
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