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I think its more likely that one of the new valves is duff, they should not need matching in that circuit. I would work out which valve causes the low gain by a process of elimination and just get a replacement for that. You would expect small variations between valves, but not as much as you seem t...

5ar4 is ok with up to 40uf as long as you keep within the limits on peak current, ensuring the series resistance and voltage limits on the spec sheet are not exceeded. I think if you keep the peak below 0.8A it should be ok (thats peak not average). Add some series resistance to the transformer as n...

In my "stash" of used valves I have a U52 rectifier. The Marconi data sheet calls it a "Bi phase half wave rectifier" ! Is that a way of saying it's a full wave rectifier ? Other data sheets say "full wave" ! Yes, I would guess to distinguish it from single phase recti...

Sorry Nick. Is "soft start" different to "slow start" ? The "potato mashers" are listed at 2A current. Who knows, its just words. Indirectly heated rectifiers start slower than directly heated ones, but both are slow compared to SS (instant). Personally if a circuit ne...

Sorry, I am not sure what you are saying, 5U4G is directly heated, but what does that have to do with what I posted?

Its a 3A heater so that may cause you a problem. GZ34/5AR4 are always a safe bet though for lower heater current.

Posted: Thu Oct 16, 2008 11:27 am Post subject: Simple Delayed Rectifier Warm-Up -------------------------------------------------------------------------------- I tried this yesterday and it seems to be useful ~ RS part No. 216-1422 NTC Inrush Limiter 2.5 Ohms (May also be described as Type S237 t...

5U4G is a good rectifier, quiet a lot of voltage drop so make sure the supply is going to give you the voltage you expect. I would expect about 50v difference between a SS and 5U4G, but PSD will let you work all that out. The soft start it gives will be a nice thing. I haven't tried the Russian ones...

Gone

Personally, I would see if its a problem before looking for a solution.

The IXCY is the simple and possibly best, but you can use a lower voltage part as Mike suggested. Just use a LM to pass 65ma, assume 20v on top of the LM, so you need a resistor on top of that to drop the extra 45v. As we know the current is 65ma its just Ohm to work out what resistor will have 45v ...

Anti-skate on unipivots (and no pivots) can be misleading, the lack of friction will make a very small force will make the arm move. I would check on a run out grove and see if there is any visible sideways deflection on the stylus.

When I built Ian's F4's he got some Ali boxes made locally with a screw down top plate. I cut holes (with a grinding wheel) in the sides and fixed the heat sinks to the reaming edge. Then he got a metal skin that covered the front and top. Hard to describe but it worked out well. The ali box itself ...

No worries Greg, the effort you are putting in is appreciated.

Sounds like the old programming aphorism. You can have software:

1. At low cost
2. That works well
3. Finished quickly.

But you can only have two out of the three.

Again this is all just a bunch of folk on the internet with opinions, I would try and get to hear something similar before spending money, but thats just me :-) The SP wound transformer coupled circuit. is much the same (see later) as the SJS one, but the 6c45p is cheaper and easier to get hold of t...