[Heath] Plate voltage SAG in Heath 221

[Wilson]

Open leg in rectifier?
Have you checked idle current on each tube (Take off plate cap.)?
60mA may be appropriate at the lower voltage.
WL


-----Original Message----- 
From: John King via Heath
Sent: Monday, October 27, 2014 4:55 PM
To: heath at puck.nether.net ; heath at mailman.qth.net
Subject: [Heath] Plate voltage SAG in Heath 221

I am  puzzled by the drop (sag)  in my SB221 when it is keyed up idling with 
NO drive. My Fluke 40 KV probe tells me that there is 2,970 VDC at the RF 
choke. When the rely jack is  grounded, the two NEW 3-500ZG tubes only draw 
60 ma. which is one half of what they should draw when keyed up and idling. 
The plate voltage drops to 2,250 VDC with only 60 ma. of idling current 
being drawn. Don't suspect the two tubes because I have installed a second 
NEW pair of tubes in the trouble shooting procedure with identical results.

I know that the metering resistor on the meter board of the SB 221 is off in 
value because it reads much lower than my fluke.

When keyed up resulting in the voltage drop from 2,970 VDC to  2,250 VDC 
there is no HUM or GRUNT indicating excessive current drain other than the 
60 ma. of idling plate current. What is causint the plate voltage drop with 
only  60 ma of idling current being drawn.

Anyone had this experience with a Heath SB 220 or SB 221 ???? If you have 
suggestions based on your actual knowledge or hands on experience, I will 
appreciate your assistance. Asking me if it is plugged in or the obvious 
will not be of assistance because I have been  breaking and fixing radios 
for 56 years. Your considered answer will be greatly appreciated. Thanks and 
73, John, K5PGW
_______________________________________________
Heath mailing list
Heath at puck.nether.net
https://puck.nether.net/mailman/listinfo/heath 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: W4BOHShack.jpg
Type: image/jpeg
Size: 1080227 bytes
Desc: not available
URL: <https://puck.nether.net/pipermail/heath/attachments/20141028/ca2ed920/attachment-0001.jpg>