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Posts by duncan1

Just a word to say I have added a stabilized  power supply using a mos-fet power transistor It is not an original design by me as there is a limit in the number of variations in solid-state design unless you make some specialized overload cut out. I used a constant current design which was pretty simple. Mos-fets are much more reliable in solid-state power supplies when used as pass transistors many normal transistors(BJT) need a lot of protection to stop them failing...
Of the working voltage of electroyltic caps that Cyril tested he found the lowest distortion on the 35 V range. Remember his own designed and built "cutting edge"[at the time ] but still good at =0.00001 % dis ability to display - Capacitors help in a specially designed jig to test with DC current flowing through them just to make thing    not only more harder but more to the point testing under near working conditions. Cyril published a series of articles on EE spread...
When my AVO VCM -tube tester went faulty till I fixed it I thought that was a temporary test   Many people have tubes that  are S/C internally its a common problem even with good make tubes. Instead of throwing then all away you could try a high voltage pulse across the S/C this sometimes "blows" the short off. You cant keep doing it as eventually it destroys the elements inside but it is always worth a try. Circuits can be seen on old tube radio repair sites. But due to...
Yiancar- Could only find the original -2007 circuit diagram. If you have 184 V on -1+2+3 then  thats the -plate- grid-cathode- all with the same high voltage. If you have swapped them around  and you still have that fault.It must be the circuit rather than  an internal S/C in the tube. You did try your MM across pins  1+2+3 just to be sure did you? If so then it sounds like the coupling caps have failed[looking at the circuit]  Thats just ONE possibility. There are more....
I agree with Wakibaki- Logic says that it  is the socket but you never answered his post - repeat-Did you try moving it about in the socket as it was playing? To me it sounds like you have bent/broken one of the contacts in the socket  by maybe pushing it in roughly . If not then you have jerked the the cable to the side putting undue force on the contacts and damaging them. 
IMO- Yes  you should buy quality caps. The ones you suggested sound good with low  ESR and metal film resistors. I always use good spec components. like -polypropylene-polystyrene - and various quality resistors.Others in the sound science  will disagree and say--"they all sound the same" not as far as I and John Lindsay Hood/Cyril Bateman[ capacitor design engineer] and others  and many here who use them too     in the high quality amps they build .  There again I am a...
I took your advice and had a look at the circuit. I can see why he wants to use -2N5486 as its used at the output of the AD8610 along with  2N5484. But I take it he is using it as a replacement  to Q 4- This is a "different kettle of fish". The voltage difference at the output of the chip is low. But if it is Q 4 then that FET straddles across the  combined voltage of the power supply and is used to balance the amp. This is a critical position and personally I would fit...
Tomb . I  take the comment you made about the bias being  able to take up to 125 MA as referring to the actual output of the circuit I was referring to the actual total current that can be used through a 2N5486 and that is certainly much less than 125 MA   in low figures. The original fet has a higher current load ability and voltage. So you are still putting in an active component that has not been designed for the original circuit--unless you have compensated for it by...
The  PN4392 is identical to the 2N4392-spec . is the same. A lot of the PN range are the same. --Mouser have them on sale at this moment-2N4392
Regardless of the outcome do you realise there is a large difference in the spec. of the 2 fets? . The one you changed the original fet for has a much  lower voltage limit and current drain limit and is meant for VHF use in delicate hf situations.. I hope you have compensated for it in the circuit? If you havent you will have a harder time balancing this.
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