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Post by trombone on Oct 7, 2023 22:09:40 GMT 12
Hi everyone,
Some time ago I asked if anyone had a circuit for this model Philips set.It is not listed in the circuit library,but it is listed in a Philips typewritten list of i.f. frequencies with the slightly unusual i.f. of 472.5kc.
It is a 5 valve 6 volt battery set,synchronous vibrator powered with the following lineup :KF3 KK2 KF3 KBC1 KL4. This is the same valve lineup as the Philips 518V (which I have two examples of ) and the same i.f. frequency.The speaker (which looks original) is an Australian Rola.The slide rule dial has both Australian m.w. and New Zealand m.w. station markings on it.
I intend to go ahead and service it using the circuit from the Model 518V until I find a difference , but I would like to hear from anyone else who might know of or who has serviced such a set.The cabinet of this set is much more conventional Philips than the 518V which has a more art deco style with big curves, which leads me to believe that this set may be a more modern- cabinetted version of the 518V possibly Australian in origin.
Thanks everyone.
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Post by pentode on Oct 10, 2023 12:09:45 GMT 12
Interesting. A lot of the sets with this and similar tube lineups were 2 volt sets with an optional conversion to 6 volts via a vibrator. Philips sold a kit for this purpose.
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Post by trombone on Oct 10, 2023 21:39:18 GMT 12
This set has the vibrator unit beside the main chassis in the cabinet, but that conversion kit sounds interesting.
I have begun servicing it and started to get my head round Philips valve socket numbering sequence - it goes anticlockwise - or at least the moulded in numbers on the valve bases do - in this set at least.I like to put a dab of twink on the socket tag No.1 to help orientate myself.
So far the circuit is very similar to the 518V. In the 518V the B- goes to earth via a 400 ohm wire wound resistor , a tap on which provides the bias for the i.f. valve and seems to be involved with the bias on the AVC line. Ducks may not be in a row there so any thoughts welcome. There seems not to be any 400 ohm resistor or if there is I haven't found it yet! R8 goes straight to earth in this 541 set and not to a tap on the 400 ohm resistor as it does in the 518V.
So far ,then , I've replaced R10 (250k but in fact 370K),R5 (50K in fact 60K )and C14 ,C13 and the volume control .I have exhumed the vibrator ,glued inside its can with pitch ,to discover that its crimping is not pristine suggesting someone has had trouble with it in the past .Getting the set out of its cabinet was tricky.One knob refused to come off and eventually only succumbed to drilling out the grub screw. And of course there is the usual elaborate Philips dial assembly (but no obvious bicycle spoke) with taut steel wire , tho' it has all come away from the cabinet fairly painlessly. We shall see what tomorrow brings.
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Post by Peter Walsham on Oct 11, 2023 8:12:39 GMT 12
Silicon Chip have just finished publishing articles (written by Dr Hugo Holden) on servicing & adjusting mechanical vibrators and continued to describe designs for some solid state replacements, using Darlington transistors & Mosfet's. His last design particularly efficient version, using bipolar transistors. See: 'Silicon Chip' June, July & August, 2023. Dr Holden discusses the design analysis & efficiencies of each of the designs in his articles. It was a particularly interesting read of these rather unreliable units.
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Post by trombone on Oct 11, 2023 13:27:03 GMT 12
Well woo hoo! It goes, not on vibrator but on the bench power supply with filament power from my 6 volt car battery. There are still two paper caps to be replaced and some of those black pitch Philips caps still to be checked. But all very encouraging.
At a recent meeting of our local VRS the conclusion was that this set was Australian in origin but a quick scan through the HRSA website seems not to list a Model 541 among Australian Philips sets.
Overall the set seems ,apart from the 400 ohm resistor in the B- line to earth,to be identical to the 518V which is the circuit I have used when referring to component numbers.
It being too cold to plant out the silverbeet plants today I retire indoors to do battle with the vibrator.Thank you Peter for your notes on electronic vibrators-that may be a path I travel down.
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Post by Peter Walsham on Oct 11, 2023 14:00:34 GMT 12
I meant to add to my message that commercially made solid state vibrators are available as well - 3, 4 & 6 Pin, 6 & 12 Volt
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