开云体育

Halden, You're quite right! You have hit on something that is thought to be a cause of certain ON/OFF switch failures in the L-4, L-4B, L-7 amplifiers and the Drake T-4X/TR-4/6 transceivers and

My homebuilt HT-37 uses diode boards in place of the vacuum tube rectifiers so that is definitely an option. My overall supply is not the original Hallicrafters design though. Uses a large TV

It's actually not necessary to restore this transformer.? I just need to not use the 5V winding.? That might be as easy as stuffing a couple diodes into the socket where the HV rectifier used to

oops ? ? edit? all. ?? dumb computer handler , I deleted that first stuff now... motors rely on air FLOW for convection cooling so don't block intended air passages with anything. these

Just a thought here. VPI'ing the entire transformer will reduce its heat dissipating capability. I once painted an electrical insulating varnish obtained at work on the exposed windings of an old

The only problem is that the circuit is inductive so the voltage and current are out of phase with each other, with the voltage leading the current.? Remember "ELI the ICE man"?? At the voltage zero

Cut a plastic milk jug that is just a bit bigger then the transformer so that the transformer can be completely covered.? Under vacuum for 10 minutes should be good enough.Jim Logic: Method used to

Jim I think you mentioned the VPI before. It likely is a good idea for a new transformer, but as the carbon track increases, there is a point of no return, or no restoration. Once the path is bad

Hi Jim, Thanks for the tip on how to make a vacuum chamber!? That sounds quite easy.? There are plenty of industrial vacuum pumps out on ebay that might pump it down faster.? Or, if one has an air

A few minutes after posting my question, I was thinking about what happens when a transformer turned on and came up with an idea: If the transformer is turned on in the middle of a power line cycle,

I had a SX-101A a few yrs back. In the process of restoring it I found that there was a large "Heating" resistor on the underside of the chasis, the purpose of which is to keep the oscillator at a

Halden Good work on doing testing and evaluation, and failure analysis. In my words, the transformer is not shorted, but the insulation has broken down, so arcing can take place at voltages well below

I have saved a bunch of EF Johnson transformers. They short like this. I took one apart and found that the short is at the end bell and not deep in the windings. I slid drinking straws over the wires

Perhaps vacuum impregnation of varnish will prevent the arc and salvage the transformer?? I have made vacuum chambers from old pressure cookers.? Quite easy to do only requiring a new gasket,

Last week, a new power transformer arrived for my HT-37 transmitter, ordered through DigiKey.? The same Hammond/Dahl transformer is used in the HT-32 series.? All wiring is PTFE.? HV wiring at the

If you mostly operate CW (as do I), did you check the "drift" on AM? Could be the BFO? TomW3TA

Thanks, Randy, for letting me evaluate the transformer from your failed HT-37! I found that all windings are isolated from each other by at least 100 megohms, as measured by a Keithley 2100 DMM.

Thanks for asking!? You questions made me look at this problem critically!? I only work CW on 40 and 20, so my remarks will be confined to that area of operation!The drift is not as bad on 20 as 40,

What is the nature of the drift? That might be a clue. Is it steady in one direction or does it drift back and forth. Does it jump (jumping is frequently due to bad silver mica caps). Can you get to

I was checking out the HT-44 operating in transceive mode on CW with the SX-117 this evening.? Monitoring on a separate receiver, I see and hear that the CW note is rough.? If I operate in "normal"