Carl Strode <[EMAIL PROTECTED]> made an utterence to the drakelist gang ---------------------------------------------------------------------- I have completed re-capping the AC-4.
After looking at the actual caps installed, and comparing it to my supply of modern electrolytics, I have replaced the 40 mfd caps (shown as 40 mfd on most schematics) with 33 mfd.
The HV filter caps were replaced with 150 mfd 450 volt units. ( I had a bunch of these laying around).
Since my original late model AC-4 had a 100 mfd cap installed at C3 and C4a, and an 80 mfd cap installed at C4b, I decided to keep everything simple and replace these with 150 mfd caps as well. I'll save all of my 82 and 100 mfd caps for some other project.
The 150 mfd caps I have are circuit board mount types, with both leads on one end. This made installation above decks a snap. I removed the old caps, and then reamed out one of the holes used for the old cap mounting screws. I installed a 1-1/4 inch long 6-32 machine screw from the bottom so it is sticking straight up near the center of the transformer primary winding. Using nylon tie-wrap, two new caps were attached to the . Just to be safe, I insulated the machine screw with some heavy-wall heat-shrink. This also provided a better grip for the tie-wraps.
I soldered the 150K resistors directly across the cap terminals.
I used a similar technique with the remaining five caps. Two caps per machine screw, and a single one for C4a.
I mounted C3 and C4b right next to each other, and soldered the big 100 ohm power resistor right across the terminals.
When I was finished, there was essentially no ripple at all! only about a tenth of a volt on the 650 and the 250 volt, and about 0.2volts on the bias supply. Oh yes, as usual nowadays, the 650 is really closer to 700, and the 250 is about 290. When the power supply is switched on, it thunks a bit harder than it used to, due to the lack of leaky caps and the increased cap values. The supply is much stiffer than before. Very little sag and absolutely no detectable hum.
I guess this demonstrates that with brute force, we don't need no steenkin regulators!
When I started, the HV was only about 450 volts with lotsa AC.
Carl Strode wrote:
Carl Strode <[EMAIL PROTECTED]> made an utterence to the drakelist gang
----------------------------------------------------------------------
I am about to re-cap one of my AC-4s.
Looking at several schematics, I note that C5a and C5b are shown as 20 microfarads.
I have a parts list dated September 1, 1974 that shows both C5s as 40 microfarads.
Looking at the AC-4 I see that indeed there are 40 mic caps installed.
What is the scoop here??
Also, I have found a bunch of new electrolytics of larger values that I am planning to use. I will replace an old 125 with a new 150 This is OK, right?
What really has me puzzled is the 20 vs 40 mic caps. I was planning on using some 33 mic caps I have on hand.
By the way, all of my new caps are 400-450 volt ratings.
Please advise.
Carl WA7CS R4B, T4XB
----------------------------------------------------------------------
On Behalf of Carl Strode <[EMAIL PROTECTED]>
Submissions: [email protected]
Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body
Hopelessly Lost: [EMAIL PROTECTED] - help in body of message
Zerobeat Web Page: http://www.zerobeat.net
Brought to you courtesy of TLCHost.net http://www.tlchost.net/
----------------------------------------------------------------------
---------------------------------------------------------------------- On Behalf of Carl Strode <[EMAIL PROTECTED]> Submissions: [email protected] Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost: [EMAIL PROTECTED] - help in body of message Zerobeat Web Page: http://www.zerobeat.net Brought to you courtesy of TLCHost.net http://www.tlchost.net/ ----------------------------------------------------------------------
