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Thanks Paul, I didn’t know what “PW Dahl-designed Hammond transformer” meant. Now I see ……… Peter W Dahl Transformers PWDAHL Series Magnetics for Amateur Radio Products This

I have no proof of this but I think the original transformers were simply poorly constructed, meaning the original supplier (Stancor ,or other manufacturer of the time) just didn't do a very good job

Just me but I dislike SS rectifier replacements for several reasons. To deal with the HV to filament winding problem, a new PW Dahl-designed Hammond transformer was recently ordered for my HT-37.

My plan would be to replace the tube rectifiers with diodes anyway. -- 73/Rick W4XA __________________________________ All posts are created using OpenSuSE Leap 15.5 x64 Linux

Tube Rectifier Compatibility Chart attached. Paul, W9AC

To minimize Vdrop, a 5U4 can oftentimes be substituted with a 5AR4/GZ34. Maximum Ep and Ip ratings between the two are similar. Paul, W9AC

The voltage drop afforded with certain tube rectifiers is definitely a factor for low B+ voltage levels.? It's the main problem in the Johnson Valiant.? (Low B+ should be around 300V and many

Rick , Re Disc ceramic caps shorting would seem rare but you never really know what a 60+ year old part will do! the judicious use of fuses even buried inside can mitigate a small failure from

Yeah....No kidding! I even took it a step further and replaced the original HT-45 plate transformer (SEC voltage 6750VAC? center-tapped) with the Drake L-4PS transformer that requires a voltage

Comments is BLUEJimLogic: Method used to arrive at the wrong conclusion, with confidence.? Murphy

Rick, Thanks for all that historical info it all makes sense, but to answer jims specific question in a little more detail the 5volt winding floats for a few cycles and then is forced to HV by the

You're right.? The additional load due to the filament current is pretty much insignificant HV choke input power supplies? used tube type rectifiers in a full wave CT configuration and placed high

All … has anyone physically looked at the off-on part of the Operation switch?. At first look one might expect it to be a wafer [ poor wafer] , but the schematic of the Ht-37 seems to show that

I don't understand how changing from a vacuum tube rectifier to a solid state rectifier has a positive affect on the power transformer's reliability.? The only difference that I see is that the load

This is a long thread, and I am very late to the party.??Maybe this has already been discussed.? HT-37 transformer failures are common due to a failure/shorting between the rectifier filament

Yup! I did say that! I was talking about Jim's mention of what a new transformer costs and I found it on Digikey! I apologize for not quoting what I was talking about! I have to say that if the

Rick, I began to think I would have to get on my knees… again and ask for forgiveness then on my last gasp of searching I found: “/g/HallicraftersRadios/message/30502 At the

If only once during the application of AC power is the issue then why use an SSR at all? The SSR forces the power transformer to see the same stress every time power is applied, the flux builds

Maybe a momentary power failure or hit could generate a similar damaging condition. 73, Maynard W6PAP

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