Ever place a non-serious bid on something fully expecting to be out-bid long before the end of the ebay auction? Yeah, I did that this morning, and won, with no competition it seems... :o
https://www.ebay.co.uk/itm/323809171531
Won for a whopping £1 (Plus £5.50 P&P). It has to be the cheapest phone I have ever won on ebay!!! :o
So what is the GPO 1/764, well, it's their early attempt at a push-button dial telephone, given that North America had established the likes of the WE 1500 & 2500 designs, the GPO thought they best have a go with a domestic button dial too basing it upon the already well-established 746, though compared to the WE phones, this was quite a kludge!! It is pulse-dial only as they hadn't discovered DTMF just yet, requires a "Battery, Secondary No.22" 4.8v battery pack* to power the dial, so no line-power ability like the later 756 (therefore, dead or no battery, no dialling ability!), and recharges said battery while the phone is on-hook...
https://britishtelephones.com/t764.htm
* https://britishtelephones.com/batsec22.htm
And it's the latter that caught my eye, given my Trimphone dial LED illumination ideas, I wanted to see how the line-chargers worked, so I saw that and thought I'd have a go at it, and, well, it's mine! ;D
Anyway, observations on the phone, the usual yellowing has occurred, for some reason the bracket on the rear that holds the shell, handset and line cables has been broken off, and of course missing the battery pack (a good thing really, leakage of old cells is bad). I can't tell if the shell is damaged as it looks like the rear bracket was snapped off with brute force, but for £1 I'm not going to complain... ;D
Anyway, obligatory auction pics time... :)
Yay, you got another phone to play with! Bargain.
A £1 fish phone! ;D
I look forward to reading more when it arrives.
Mine (8756) was yellowed too, I chemically sanded it:
http://www.classicrotaryphones.com/forum/index.php?&topic=20579
Your battery comments got me looking at my 1983 version. At first glance, from the top view, it could be mistaken to be the same phone, so if I may, photos of the 8756 base and interior for comparison:
I really wasn't expecting to have won that phone, so I'm rather pleased with the price, and it's got features I've not seen before so it's something new to play with... ;D
Also I just realised I called the 756 the 754 (no such model existed!), corrected that error now!!! ;D
It'll be interesting to see the differences between the 756 and 764, though one obvious thing, there's a lot less spaghetti in the 756, but as I said, the 764 was a kludge of a phone, given a battery really wasn't needed as the technology for line-powered button dials existed, though I am interested to see how they put together the electronic parts for storing the button presses, given the 70s was the start of the microcomputer boom era...
And as for whitening, I bought a bunch of 1 Watt Royal Blue LEDs (useable for UV exposure as they emit near-UV light) last year which can be used for indoor peroxide-whitening, so may assemble myself an exposure box with the LEDs inside, I have a number of yellowed plastics I would like to whiten, I just haven't gotten around to making a suitable setup yet... :)
I just posted in the Trimphone thread about these phones with the battery inside. I didn't know they recharged. Am I remembering right that some phones had a blue battery and some had a red battery, which was different somehow?
Good luck with the experimentation. I'm looking forward to someone coming up with a way of powering a trimphone dial.
Incidentally, don't later model US Trimline phones have an illuminated dial powered by the line? I know early examples had a mains powered transformer and tungsten bulb, but from what I've read the later ones had a line powered LED of some kind. One of those might give some clues on how to light a trimphone?
Unfortunately US Trimlines are very few and far between over here.
The battery difference is Red (Battery, Secondary No. 22) = 4.8 Volts, Blue (Batt. etc. No.23) = 7.2 Volts, and denoted by the phone model, 1/764 being No.22 and 2/764 being No.23... :)
Plenty info on the phone in the usual place on the phone and its' charging arrangements (can be line, can be a local 50v supply):
https://britishtelephones.com/t764.htm
(I should have posted that initially but I forgot!)
I'm looking forward to seeing how it works though, I knew of them but never really looked into getting one of these phones for interest purposes, but with the thoughts on Trimphone dial lighting it just popped into my head when I saw this particular phone for sale, I guess it was just fate that my not-serious bid actually won it for me... ;D
I was hoping the phone would have arrived today though, but unfortunately not, have to wait until Tues. with it being a bank holiday Monday... :-\
As for the Trimlines with LED-lit keypads, I presume they only light when off-hook (as on-hook they're sat in their base cradle), so are presumably taking power from the line when in use, and when on-hook, they're cut off so they don't take a hit from the 48vDC line power, that's all I can deduce without knowing though... ???
Quote from: twocvbloke on May 25, 2019, 04:49:55 PM
As for the Trimlines with LED-lit keypads, I presume they only light when off-hook (as on-hook they're sat in their base cradle), so are presumably taking power from the line when in use, and when on-hook, they're cut off so they don't take a hit from the 48vDC line power, that's all I can deduce without knowing though... ???
I think you're right. I gather a Trimline only lights up when off-hook. I don't actiually have one (yet) so can't tell you much about it.
Well, seems Hermes delivers on a Sunday, as the phone is here, haven't taken pictures as yet, but am presently fondling those buttons, ooh they have a nice feel to them, almost akin to an IBM model M keyboard, but without the clicky sound, really nice action on them... ;D
Need to grab the N-diagram for it as there's a couple of loose wires which I've no idea where they go, and of course the rear bracket needs a replacement from somewhere, but overall it's in reasonable shape, which for £1 is an absolute steal!! :D
You should nominate it for find of the month.
I hadn't thought of that, certainly been a find for me, just working out how to fix it at the moment... :)
Just been taking pictures (not processed them as yet) and taking the phone apart, and I've noted a few things about it...
One is a Mercury Wetted Contact Relay, definitely something you wouldn't see being used today!!
There were no feet or a rubber plug in the auxiliary wiring hole, which leads me to believe this was actually used atop an N625 base...
The dial, I can't work that out, there's no IC on there (not surprising) so has to be entirely run through the various transistors, diodes, capacitors and resistors, very complex, and confusing, I don't dare even think of taking the dial apart!!!
The handset is outfitted with a blue Transmitter 21/A which I believe is Rathdown Industries...
I decided my chocolate brown 740 is to be parts, considering when I took its' case off, the cracks I'd glued up broke apart again, so, the shell's just spare plastic I guess, and I'd previously nabbed some innards already, so, parts phone...
Drilled out the remains of the bracket from the 764, and removed the 740's in the same manner, had to file down the smallest of my pop-rivets to fit through the holes in the base plate, and the bracket holes needed opening up somewhat to accept said rivets, but that attached nicely and looks pretty good if I do say so myself, haven't test-fitted the shell as yet as that and the other plastics are presently having a bath, as is the handset cable which is pretty stretched out...
About all there is to report so far, and now I'm quite hungry so I shall get myself some food, then work on processing the pictures... :)
Thank you for posting the pictures. Big difference in design for the dial! I'm so used to WE equipment that seeing a GPO phone is really a treat! the keypad is soooo huge! wow!
I just got the phone back together, and now I want to grab one of my 2500s to compare dial sizes now!!!! ;D
Still not done my pics yet though.......
And at long last, pictures, taking it apart pre-washing and noting a few details of the phone:
And 2nd lot of pics, replacement of the bracket, addition of feet & aux. wiring plug (and the addition of a scratch from some berk with a screwdriver!), a home-made screw retention nut made from a large, cut-down, filed and threaded rivet, and lastly the final thing, even though I haven't actually wired it up yet, and a chocolate brown handset sat atop it... :)
(last two are just bigger versions of two in set H for clarity)
Oh I hate that when that happens... a piece breaks off and its part of the housing... so frustrating fixing parts like that!
I haven't a clue how a previous owner broke that off, I mean, they'd have to be a complete idiot to not know how to use a flat-headed screwdriver to remove a screw!! As for the missing retaining nut, that's common, I just had a random thought on how to replace it, and it seems to work nicely... :)
I just got woken up mid-dream right at the perfect point, I'd come up with a new dial card with a suitably nerdy number that went along with the unreadable original; 01-486-6502... ;D
Getting a Transmitter 21A is a nice bonus as they are getting quite hard to find now.
:)
I've a few red 21As around, this blue one is a new one for me though, even though they're technically the same thing... :)
Totally random picture but I just noticed my Twitter posts number, rather amused me... ;D
Quote from: twocvbloke on May 27, 2019, 04:14:24 PM
I've a few red 21As around, this blue one is a new one for me though, even though they're technically the same thing... :)
The red ones are arguably more useful as you can use the inner 'capsule' in other phones, but they're all far better than the carbon granule versions.
:)
So long as the red ones actually had the correct innards, as three of mine turned out not to:
http://www.classicrotaryphones.com/forum/index.php?topic=7254
Only just remembered about that little discovery... ;D
Quote from: andy1702 on May 26, 2019, 07:24:23 AM
I think you're right. I gather a Trimline only lights up when off-hook. I don't actiually have one (yet) so can't tell you much about it.
Yes, Trimline phones only light up when the phone is off hook, with the LED models being line powered. Later post breakup Trimline phones with memory dial functions do use some line power to keep their memory going, though I don't know the specifics of how they trickle this from the line power. They do not have batteries, but a capacitor in the phone will bridge the memory through brief power interruptions like unplugging and moving the phone.
Just been driving myself nuts with wiring this phone back up inside, it's really been messed with in the past, had to pull it all and re-do it from scratch, then found it was missing an auxiliary gravity switch (19B-1) "to control the push-button unit" as the N864 diagram states, thankfully I bought some 36A-1 switches last year, there seems to be conflicting info as to which switch is what poles-wise, but as the dial only needs a single-pole changeover switch, the 36A-1 will work nicely...
Next step, battery, I daren't use a 4.2v Lithium Polymer battery I have spare, just incase something goes wrong, so, I'll have to have a look about to see what's available on ebay... :)
I'd take some pictures of the wiring, but, I'm so sleepy right now I'm falling asleep as I type, I need to go to bed!!! :-\
Finally got around to getting the additional pictures, 1st showing the Switch 36A-1, took a fair old amount of adjusting to get it to work in time with the main hookswitch, plus a view of all the extra wiring required to operate this particular dial.
2nd, the terminal arrangement as originally wired per N864, with the only difference being the 3.3k resistor in line with the ringer coils.
3rd is showing the back of the extra terminal strip showing a capacitor (I believe) between a couple of terminals.
And lastly 4th is showing some battery leakage damage I didn't notice previously, but it's nothing that really concerns me that much... :)
Plus an extra bonus clip of pressing the buttons, sadly my mobile isn't that good at picking up the rather joyously satisfying feel of the clicks the buttons make, but it's still something to watch nonetheless... ;D
https://www.youtube.com/watch?v=HmP05ZKPgc0
Is the relay a part of the "push-button unit assembly"?
Is there a circuit for that?
Thanks
Jack
I believe the relay takes the place of the pulsing contacts in a regular dial, so the phone presumably clicks as it dials the number, I haven't tried it out yet as I've yet to power it up with something suitable... :)
Quote from: twocvbloke on June 02, 2019, 01:38:03 AM
I believe the relay takes the place of the pulsing contacts in a regular dial, so the phone presumably clicks as it dials the number, I haven't tried it out yet as I've yet to power it up with something suitable... :)
Ok, I thought it might have been the ON contacts. I don't remember seeing a relay on other LD button phones. But then, I don't think anyone else used a battery either.
No circuit for the keypad logic?
Jack
Quote from: Jack Ryan on June 02, 2019, 02:30:04 AMNo circuit for the keypad logic?
So far I've not found any diagrams for the keypad, as I too am curious as to how it works, it appears to be all individual transistors providing the logic as I can't see an IC of any kind on the keypad (not that there would be given the era, ICs would probably have been quite expensive in the 70s and reserved for computers only), the only circuit I have available is the one from the N864 diagram, which only depicts the inputs to the dial which is just a big empty box... :-\
Quote from: twocvbloke on June 02, 2019, 03:44:49 AM
ICs would probably have been quite expensive in the 70s and reserved for computers only),
WE made some trimlines with tone generating chips as early as 1968-69. These were both 10 and 12 round button sets.
Most of the early handsets were potted TT pads, but they concurrently made the tone generating IC pads .
By the mid 70's many of the round button sets were being rebuilt with IC's. There were many sets that were rebuilt with potted TT pads as well.
The earliest tone generating IC chips were clear
The picture phone project was concurrent and also used a lot of IC chips.
Jim
As a side note regarding trimlines, the round button sets seemed to continually evolve and the boards changed quite a bit. You can find a lot of variations in the handset layout. The handsets on square button sets pretty much stayed the same, tho they were simplified as time went on.
The GPO was still quite archaic (they stuck with mechanical exchanges for far longer than the US) when the Bell System was already releasing Touch Tone dialling telephones, as far as I'm aware, TT, let alone push-button, didn't become a common thing here in the UK until at least the 1980s after the GPO was split into The Post Office and British Telecom, and the latter had to basically start becoming more technologically advanced than it was under the GPO's rule... :)
And as for electronics, the typical "that'll do" thing tended to be the staple here, transistors did the job & were cheaper to obtain, so "that'll do", given that an appropriate IC could have been used to generate dial pulses and have been a far more compact solution, but they didn't use that sadly...
But still, it makes our telephones somewhat unique in the way they stuck with what they knew for so long, but that they also designed them to be long-lasting and therefore still working today, give or take a few repairs or additional parts... :)
Finally dug out my PAP2T to test the phone, and it's not ringing!!! Either I've fluffed up the wiring, or there's something wrong, presently just going through the N-diagram now to make sure I haven't missed anything or wired it up incorrectly... ???
Also being driven nuts by someone running a two-stroke engined something outside really loudly......
EDIT:
Never mind, it was a PEBCAK with my wiring in the Block Terminal... ::)
I decided to brave using a protected LiPo battery (4.2v fully charged, compared to the 4.8v of a NiCad or NiMH, hence the need for protection), and hooking it up to the battery connector, the dial has come to life!!! ;D
The battery is being charged at a low current of 2.8mA, so shouldn't cause the LiPo to go pop, so not too much of an issue there, though I think the LiPo needs slightly more to be properly charged, but I'm no expert and frankly I don't want any flames in this phone thankyouverymuch... :o
Anyway, dialling a string of numbers, the mercury relay does some very quiet clicks at a reasonably proper 10pps rate, so quiet I doubt the stupid noise-gate nonsense on my mobile phone's camera would allow it to be picked up, so need to think about how to record that, but I'm rather happy to hear it ticking away as I push buttons... ;D