Looking for someone very knowledgeable on the Henry 2KD Classic

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KU8L:
Thanks Gentlemen:

I wasn't ignoring you, just really busy here.  I'll be checking all of the suggested points.  I even reached out to Henry to ask about sudden death issues with their diode stacks--no response. 

I have checked the B- rail clamping diode and found it good.  I really see no other mechanism that would cause enough current to open up the bias diode other than a grid/filament short or a ground fault in the filament circuits..none of which I have found. 

I have the tubes out now and they test OK but I may try another pair if I don't find something else.  THe sockets, bypass caps, an the transformer all seem OK but I did not hi-pot the transformer.

I am going to replace the main 3A 100PIV B- clamping diode just for safety--I wonder why there is a second diode in parallel to this one on the metering section--same wiring but much lighter rating.

Yes there were the proper bypass caps on the bias diode when replaced.

I plan to put in one of the 10 or 12V 50W zeners for the bias.  These are real zeners and will be installed reverse pol.  Henry docs are very confusing because the call the bias diode a zener in some places but it is really a silicon rectifier stack--so installed fwd direction. 

At that point, I'll be able to record more data on the various dynamic conditions with power on.

More to follow.

Curt

DMOD:
Quote from: KU8L on September 19, 2018, 10:17:05 AM

Thanks Gentlemen:

...I am going to replace the main 3A 100PIV B- clamping diode just for safety--I wonder why there is a second diode in parallel to this one on the metering section--same wiring but much lighter rating...


More to follow.

Curt


D105 is a 100V, 5W Zener that supplies the ALC circuit.

Safety diode D106 is a 100V 3A type or a 1N4720.

D107 is a type 1N4004 diode and is in series with the Ip meter and in series with a fuse and is shunted by a 150 ohm 2W resistor. There are no diodes in parallel with D107 or shouldn't be. The meter is in series with the bias circuit to measure plate current.

See the attached PDF file:

Any time I see a diode string used as bias it gets replaced by a zener for the bias  needed.

Phil - AC0OB

KU8L:
Like I mentioned, these are the worst schematics I have seen in a long time.

The Henry schematic I have dated 11-16-88  pvp  Shows D107 inseries with the Ip meter and R129 and the anode is shown tied directly to Ground  The cathode end is tied to the lower end of the .1ohm resistors AND the B- rail. (shown as Pin 2 of TB101 but the note says there is no TB101 in the KD version and wired direct)

Someone has clearly been inside this one and it appears some wiring was removed and resoldered.  in the area of D107.  I will have a look at it to see if they may have put it back to match this schematic which may be in error.  I'll post the PDF of this schematic in the morning so you can see it.

I do have a differnt schematic from a different version of the manual that shows the 2KD Classic PS and metering on the same page.  It is layed out like you diagram.    The one I referred to above has three pages--one for RF deck, one for the PS, and one for the metering.

Thanks

The serial number of this amp is:  54-427.   Sure would have been nice to have a indication on the manuals of range of serial numbers if they have different manuals.

Curt

DMOD:
I think the schematics are straight forward.

You have to determine what unit you have.

The 2K-Classic power supply has a C filtered power supply with a string of equalizing resistors across each Cap.

The 2K-ClassicX has a resonant choke power supply with a single HV capacitor.

The 2K-Classic has R119 across Diode D107.

The 2K-ClassicX has R115 across Diode D107.

Find out what unit you have and follow the specific power supply schematic.

In either case, the meter steering diode D107 goes to the B- rail.


Phil - AC0OB

KU8L:
Hi Phil:  SOME of the schematics are fine.  Others not so much.  Diodes shown backwards, call outs for Zeners that aren't zeners, Zeners that are shown as diodes, etc. 

THe unit says 2KD-Classic on the label.   I don't know what year it is but ser no is 54-427.  Here is the front and meter schematic I was given with the unit.  I note the ser number on the front in handwriting is (maybe) much earlier--and the ID on the download was 1988manual-B.  Note the ground added to the end of D107.  This schematic looks like a 8 year old made it.

SO I am going to try to tell if the schematic you have referred to is (likely) the more correct one. 

I appreciate your patience and your help on this.  I'm doing this as favor to a friend but it had been in someone elses repair hands prior and not working--they just gave up.

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