I bought a Linesman telephone...

[twocvbloke]

Just tried out the kitchen phone, and there's not enough power to even let the phone dial, blowing into the phone results in a weak crackling in the linesman phone's handset, so, yeah, I'm at a loss.

[russell_w_b]

Originally Posted by twocvbloke

With my meter set to 10A, the phone, with or without the Viscount connected, uses 0.02A, and when ringing, it uses 0.35A...

Sounds reasonable, though your ringing current seems high for a Viscount. The one I have at work draws 21mA on CB, decreasing to 10mA with the mic energised. On 'Ring', it draws 200mA into a 2k2 resistor, and 140mA on open-cct. Have you checked all battery connections for dirt and made sure they're clean? If so, check your switch contacts as well.

- And don't be taken in by the simplicity of your 'ornery piece of metal' dial either... This is how they are maintained (yes, I know one can tap out numbers on the cradle...)!

[twocvbloke]

I didn't measure the ringing current on the other phone (an audioline somethingorother) as the batteries have worn down below 3.5v, but all the connections I've gone over inside the linesman have been clean, almost brand new infact, the only bad bit was the battery cap which was corroded, but I've scrubbed that up to a shine, the only bit I haven't shined up is the inner ring that connects the cap to the positive wire, need to dig out the dremel-tool (well, dremel style tool) and give it a wire brushing, but as it is, it looks fine, but I don't know, it's all rather confusing.

As for the dial, yeah, that looks fun, just a good thing it's in pretty much perfect condition! I don't fancy stripping one down to clean up and fix.

[twocvbloke]

Dunno if it means anything, but the ringer assembly coils, which say "500Ohm" on them each measure as 272Ohms, I've completely forgotten what I learned about Ohms and resistance, so, I'm not sure what that equates to....

[russell_w_b]

Originally Posted by twocvbloke

I didn't measure the ringing current on the other phone:

I ought to make clear I was metering the d.c. battery supply whist ringing (three hands needed! ). 2.2k is near enough the load impedance of a magneto telephone bell without the capacitor in series (sort of varies between 2.46 Z and 2.62 Z, depending on which particular bell-motor one is using). I suspect a 'Viscount' will draw less, having a lower REN, but, in any case, the ringer still draws 140mA on open-cct.

I guess if battery consumption is a problem with continued ringing and the subsequent current-drain, you could always lash up a 4.5V PSU instead.

[twocvbloke]

I did the same with the Viscounts last night, using the multimeter in place of the battery cap, but measuring the voltage today, the batteries had been drained (and I did remember to set the phone to CB, I've read about leaving them on LB and the batteries bursting or leaking!! ), so I didn't see the point in measuring current on low batteries.

I'm considering a 4.5v PSU, just need to work out where to get one that can supply the mA's for the odd power issues.

[twocvbloke]

Another issue, the metal strip on the battery cap is desperately thin, due to corrosion, looks like that 4.5v PSU is looking more and more likely.

Unless, I could rig up a battery pack using those 4.5V batteries with the metal strip tabs on the top, two wired in parallel strapped together, shouldn't be too difficult to achieve.

[AndiiT]

Hi, the voltage on these linesmans telephones doesn't seem to be too critical, I "modified" the one that I have, which had no battery door cover, to use a 9 Volt PP3 type battery with no extra series resistance and it seems to work fine.

Andrew

[russell_w_b]

Originally Posted by twocvbloke

'...Dunno if it means anything, but the ringer assembly coils, which say "500Ohm" on them each measure as 272Ohms...'

Were you measuring the coils in isolation, or might there have been something shunting them at the time?

[JCM3000]

[QUOTE=twocvbloke;371551]As for the dial, yeah, that looks fun, just a good thing it's in pretty much perfect condition!!! I don't fancy stripping one down to clean up and fix.

One of my favourite parts of doing a 'phone up.

If I remember correctly, one rail of a standard PC power supply provides 4.5v, not sure if that would work though.

[twocvbloke]

Originally Posted by russell_w_b

Were you measuring the coils in isolation, or might there have been something shunting them at the time?

I was measuring them with the batteries disconnected and the switch set to CB, I daren't take a soldering iron to them just yet, just in case.

I did manage to make the buzzer louder though, seems the locking nut on the tension spring adjuster came loose and it left it a bit limp and pretty quiet, but I've managed to adjust it so it's nice and noisy, shame there's no room for bells in there though, that'd sound nicer.

I've noticed something about the voltage though, seems measuring at the line terminals yields a lower voltage than if I measure the batteries directly, while tinkering with a 20v panel meter of mine, the line voltage was about 3.5v, but the battery pack voltage (with the phone assembly removed) was correct at 4.5v, with no load of course, I'm just wondering if there's some component that's given up the ghost or something, and I'm not sure where to look.

[twocvbloke]

Originally Posted by JCM3000

One of my favourite parts of doing a 'phone up.
If I remember correctly, one rail of a standard PC power supply provides 4.5v, not sure if that would work though.

The one thing that concerns me about attempting to do anything with the dial in this linesman phone is that the assembly is plastic, and not metal, and I have a bad habit of stripping the threading in plastic things.

I'll have a look into that PC power supply, got a spare 250w one somewhere that isn't any good for my main desktop PC, could be useful.

[russell_w_b]

Originally Posted by twocvbloke

'with no load of course'

No doubt you'll have studied the circuit diagram here. It will be seen that between the battery and the test-terminals are an inductor and a 27R resistor. Your battery, however, will be loaded by the mic cct (remember you're in LB mode and you need to provide speech current to your local mic), and your readings are commensurate with what I get on my instrument.

[russell_w_b]

Originally Posted by twocvbloke

I was measuring them with the batteries disconnected and the switch set to CB, I daren't take a soldering iron to them just yet, just in case.

Bet you had your 704 off-hook, though - ah-HA! Think you'll find that when off-hook, the bell is shunted by the regulator components and the induction coil and 150R resistor R1 in series with them. When you replace your handset the 'bell' bobbins read 1000R.

Make several drawings of the circuit from the link I gave you in another post and draw out, on each drawing, in different colour pen your telephone currents for different working conditions.

[twocvbloke]

Yep, seems I measured with the handset off-hook, on hook they each measure 510Ohms, and together they measure 1019Ohms.
As for the circuit diagram thing, erm, I'm never been one for reading them, it took me 15 minutes just to work out where the bits you were talking about were located on the map, and a little longer to find the (rather small) battery symbol.
(and yes, I'm just as bad with geographical maps too!!!)