[Central-Electronics] 100V-200V Cabinet

[Jim Candela]

Ray,

   I looked at the 100v service manual and here is what they say:

"Poor sideband suppression is generally caused by ''open'' 6 mfd
50V electrolytic capacitors in the plug-in hid CAPS assembly.
If the modulator capacitors appear to be good, remove the PS-2
and take off the cover. Using a long none pliers, gently pull
on the leads from the mica capacitor that go to the board.
During the original soldering process, the hot wax from the
capacitor case will run down the wire leads to the board and
result in a poor connection.

This treatment should also be applied to the leads that go into  
the 9 prong plug to see that the connections are properly soldered.
Early 100V's   used 3990 ohm, 1 watt, 5% resistors in the plate
circuit of V10, the 12BH7, R146 and R149. These are generally
located underneath the 12BH7 socket, with one end tied to the
center shield. lf the case is discolored on the resistors,
cheek their value and replace with 2 watt 5%, if necessary."

Hope this helps,
Jim
WD5JKO


  ----- Original Message ----- 
  From: brockhouse raymon 
  To: central-electronics at mailman.qth.net 
  Sent: Friday, January 16, 2009 7:39 PM
  Subject: [Central-Electronics] 100V-200V Cabinet


        I am looking for a 100V cabinet. Let me know what you have?  I have a 100V & a 200V, on
        the 100V I can get both sidebands nulled perfect but on the 200V LSB is good and USB not so good or the other way around. I have matched MOD CAPS and Silicon matched diodes. 
        The 2 caps in the PS2 off the plate feeding the PS2 were leaky on both units. One was 4710pf and the other 1850pf. I used 2 silver micas for each to get the proper size and checked the size on a CAP. meter. This worked perfect. If you have a different voltage than 
        .8 votls on the grid of the tube following the PS2  I believe these caps are probably bad. Two of them measured 80 megs on a VTVM but the other two were above 100 meg but replacing them fixed the problem. Both of these CAPS were bad on the 100V & 200V.  Any ideas on getting both sidebands equally down? Thanks.
        Ray


           




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