SX-101 trouble

[PAUL PAGEL]

Bob, I think you should first concentrate your search at the power supply. With such low filament voltage nothing's going to work right. Remove the load from the power supply and check the AC output voltages of the power transformer to ensure it's delivering the correct high voltage each side of center tap and the proper 5 and 6.3 V filament supplies. Once you know that the power-supply transformer is working correctly (it sounds like it's not) you can start troubleshooting by plugging in the 5Y3 and see what plate voltage is available, then go from there.
 
73,
 
Paul / N1FB

t Keeble <kg4nvx at IGILES.NET> wrote:
Need advice from the group!
SX-101 Mark I. Was not receiving when I got it but could hear very faint 
signals through atmospheric noise.
Replaced all Black beauties and Red Chiefs and can lytic.

* Radio powers up with atmospheric noise but no signals on any band. 

* Signal from generator applied to antenna input shows up at antenna
coils and changes with band switch and signal generator frequency
to show up at proper ant. coil.

* Signal also shows up at mixer coils at higher level.

* Signal does not show up at Osc coils.

* No signal heard at all when tuning across the dial on any band.

* With outside antenna (only at night)... multiple broadcast
stations heard at the same time but tuning up and down the band
has no effect. Activity is louder on 160 and weaker as I go up to
80 , 40 etc.

* When measuring tube voltages I am getting only 2 VAC on all tube
heaters when it calls for 6.3 VAC. Also removed the 5Y3 Rectifier
and and measured across the heater secondary and read only 2 VAC
directly from transformer. (Secondary 6.3 leads show evidence of
overheating, right near the 5Y3 socket)

* All plate voltages check low, some lower than others. Worst are
1st RF amp *160, should be 210,* 1st mixer *180, should be 240*, 
1st IF amp *175, should be 210* * *1st conv oscillator/cathode
follower *130, should be 150* and at rectifier* 220, should be
280.*
* *Grid voltage on 1st conv/osc shows zero on pin 2 and 7 and should
be -12 and -4 respectively.*
* *Dial lamps appear to be dim to me (dull orange)
*

Could the transformer be weak enough that the later stages are affected 
more than the earlier ones?
Have substituted known good tubes for most all of the existing except 
for the 6BJ7 Det/ANL/AVC. (don't have a spare)
Any thoughts will be appreciated, Bob, KG4NVX

KG4NVX at igiles.net

-----------------------------------------------------------
Products bought, sold or traded here is the responsibility of the
parties involved. This list and the City of Tempe are not responsible
for losses or misrepresentations of any kind. Buyer beware!

-----------------------------------------------------------
This list is a public service of the City of Tempe, Arizona
-----------------------------------------------------------

Subscription control - http://www.tempe.gov/lists/control.asp?list=HEATH
To post - HEATH at LISTSERV.TEMPE.GOV
Archives - http://listserv.tempe.gov/archives/HEATH.html



-----------------------------------------------------------
Products bought, sold or traded here is the responsibility of the
parties involved.  This list and the City of Tempe are not responsible
for losses or misrepresentations of any kind.  Buyer beware!

-----------------------------------------------------------
This list is a public service of the City of Tempe, Arizona
-----------------------------------------------------------

Subscription control - http://www.tempe.gov/lists/control.asp?list=HEATH
To post - HEATH at LISTSERV.TEMPE.GOV
Archives - http://listserv.tempe.gov/archives/HEATH.html