Re: Old Heathkit Ham Linear Tube Amplifiers .... Mods, Repairs, best Refurbishment practices ?
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Watch out for failed dropping resistors for the metering circuit for the high voltage. IIRC they are 4.7meg. Replace them with metal oxide 3W in place of the 2W ones there. I would do that anyway even if those old carbon comp resistors measure okay. Needless to say the HV supply can kill you quite easily!
Sam Reaves
ARS W3OHM
Owner / Moderator of: LeCroy Owners Group on Groups.io
Sencore Owners Group on Groups.io Sprint Layout Group on Groups.io?? Pulsonix EDA Group on Groups.io
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Electronics and Mechanical Hardware Design Engineering Manager
Staff Scientist Andritz Rolls Global Research Center (RETIRED)
Hoping to stimulate some discussion on Old Ham Tube Linear Amps:
? Are there any experienced with the various Tube Amp issues,
???? ... such as Arcing and Band SW,? coil,? capacitor & tube and HV Xfrmr destruction in these amplifiers ?
I am beginning to refurbish two old Heathkit Linear Amps:
?? the SB-1000? ( similar to the AL-80)?
& the SB-200.
? Scouring the Web looking for information on refurbishing issues and modifying old Heathkit Ham Linear Tube amplifiers
quick summary:
PS Cap board
Metering board /Bias
Soft-Key
Soft-Start
Parasitic's
Glitch resistor
HEC HV Caps
Self-biasing of relays
"Corona Washer "
QSK
new tubes ...
poor solder joints (expected)
Band Sw issues,
etc.
There are plenty of Ham Blogs on the SB-200? & SB-220,? ...? but fewer on the SB-1000 & HL-2200.
?Articles by Richard Measures, and others, some with theory, discussion, diagrams, photos ,
??? and, as with anything,? some miss-information and some corrections.
There are a lot of YouTube videos,? and ? AmpRepairGuy.com?? has some videos of his repairs.
? Likely others , all requiring sifting the information and reasoning.
Harbach Co.? & CTR Engineering? Kits,? parts for? Mods (depending on the Amp Model):
? Having good instruction,? kits, ? PCB's ?? and downloadable .pdf's at both of these? two? web sites:
Possibly the Richard Measures (SK) Amp Forum, has some priceless,? sometimes buried help:
The "search" bar? { below }? can still dial in the query:
example:
And,
? ....? there seem to be some PCB's? from?? W7RY , although I have not been successful getting adequate answers or actually purchasing the PCB's
thanks,
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Sam Reaves