@marconi_mpt4 a quick look through my valve database shows 7 off 6x4's they will all be pulls untested but hopefully these a good one
Cartridge is yellow bodied no markings but fitted with a ST12 stylus
Again, a picture would be appreciated but it sounds like a BSR X3H - my little Fidelity HF31 (my first record player) used one. I'd have expected an ST8 stylus in that though?
Danette had a posh version with a transformer.. 
I am a bit puzzled as looking at the pictures I cannot see any surge limiting resistor between mains input from the switch terminal to both anodes which look as if they are wired in parallel. Is there one hidden away? EZ90 / 6X4 data suggests a minimum of 470Ω.
Rich
Probably relying on the lower HT and transformer windings, my Mullard book states 520 Ohm per anode. They probably were hoping it lasts the 3 months guarantee that valves had then, it could be passed onto the customer as their problem.
Edit. Thinking again about it, the valve maker would be responsible for replacement so they must have been happy with the circuit, perhaps?
Frank
I am a bit puzzled as looking at the pictures I cannot see any surge limiting resistor between mains input from the switch terminal to both anodes which look as if they are wired in parallel. Is there one hidden away? EZ90 / 6X4 data suggests a minimum of 470Ω.
Rich
there is no surge resistor so will add one what sort off wattage ?
Cartridge is yellow bodied no markings but fitted with a ST12 stylus
Again, a picture would be appreciated but it sounds like a BSR X3H - my little Fidelity HF31 (my first record player) used one. I'd have expected an ST8 stylus in that though?
a little out off focus
Mod Note: See mod advice on following post below
more pics and some more info
no surge resistor on the 6x4 so will add one
the mains transformer is only for the valve heaters and only one primary voltage as no tapping's
the 1/2 meg vol/power switch does not switch on .As this is a live chassis I will change both pot (vol plus tone)
to newer versions with plastic shafts and make sure neutral is to chassis
there is one waxie and 1 red/yellow elec cap so will replace both Main dual can elec is very leaky so will need restuffing/replacing.
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It's a bit out of focus, but that cartridge definitely looks like a BSR X3H.
OK I should know but is the X3H cartridge crystal or ceramic?
Frank
Thank you, not had a record player for 20 odd years and that had a magnetic cartridge of some sort, it would be the 1970’s when I replaced quite a number of cartridges and styli.
Frank
A typical surge limiting resistor would be in the range of 4 to 5W but before I can comment further, what is the value of reservoir capacitor used? At the moment have assumed 16μF for calcs.
Rich
A typical surge limiting resistor would be in the range of 4 to 5W but before I can comment further, what is the value of reservoir capacitor used? At the moment have assumed 16μF for calcs.
Rich
as the dual can cap is very leaky i will have to replace it will need to dig out my box of spares and see what fits size wise. and then what values it has in it
will report back
final had a little more time last night
the main smoothing cap is a Dual 32uF with a 1500R res between the 2 positives
basic pars list to help anyone in the future
There is a 1/2 meg volume pot/switch and 50K lin tone control neither look original as both shaft are somewhat hacked
A 25v 25uF red yellow elec with a 120R resistor across it
And a waxie 0.005 350V
and the 2 valves
I would be inclined to change that red/blue electrolytic cap (the one with the yellow label). As I recall. these were not the most reliable of caps, and we (granddad) replaced a tidy few in the early 70s, radios mostly, but it was always these caps that came to attention.
there is no surge resistor so will add one what sort off wattage ?
One of the most informative data sheets for 6X4 was published by General Electric and includes various graphs. Link here http://r-type.org/pdfs/6x4-1.pdf In particular rating chart III on page 4 illustrates minimum limiting resistance required versus input voltage. At 240V RMS the resistance is shown as approximately 180Ω and absolute maximum surge current under any circumstance is 1.1A. Using a very accurate 6X4 SPICE model it was possible to simulate peak current not only for different resistance values but also for using two resistors, one to each anode.
No surprises here, the existing circuit permits surge current to exceed rated absolute maximum by roughly four times (highlighted yellow). Using the recommended 180Ω per anode configuration the peak current agrees with data sheet value (Highlighted blue). However a single 180Ω resistor with diodes in parallel works fine but results in lower voltage output. When using diodes in parallel, to reduce this loss simple reduce series resistance to 100Ω and keep within maximum surge current rating (highlighted green).
Rich
Mod Note: Fixed quote
Do the calculations take into account the resistance of the secondary transformer winding?
Frank
Yes you would normally expect the transformer to have a HT winding, but to quote an earlier post by FIXITNOW2003:
"no surge resistor on the 6x4 so will add one, the mains transformer is only for the valve heaters and only one primary voltage as no tapping's"
Based on those findings it appears to be configured without any surge limiting resistance or inductance and so calculated limits from that.
I question if this really was an original configuration or if the HT transformer had been later replaced with a heater only version. Valve types would suggest a design for isolated chassis. Now as this is a live chassis, is the pickup wiring isolated?
Rich
