12-31-2018, 12:22 PM
The 16b chassis that I pulled from the attic is missing the two electrolytic cap cans at the rear (#87 & #88) and there are a few (3?) stray wires as well.
The attached pic shows the current situation.
Green arrow points to the lead from the center tap of the power transformer. This is 400 volts, correct?
My understanding is that this goes to the two cans at the rear and then to #75 (10 uF, 50v).
1. Does this lead go to the center terminal of the cans or to the outside? For all three cans? Or is the wiring reversed for #75 (pos. chassis ground)? Are there jumpers to make the connection (in an original set)?
White arrow points to two leads running from two side tabs on bakelite cap. #86. One has a terminal (not shown); the other appears to have been cut.
2. Same question as above: In an original set do these go to the center terminal of the cans or to the case? What is the polarity? (Positive? Because the center tap on the xfrm is negative?)
3. Since the cans are supposed to be insulated from the chassis, I assume that this is the reason that the neg. chassis ground on #87 & #88 does not short with the positive chassis ground on #75 -- or am I all wet?
Red arrow points to a cap (value unknown) that appears to have been retrofitted at some point in the past. This appears to be wrong for a number of reasons: (a) it does not conform to any part of the schematic for #87 or #88, which are connected to the center tap of the transformer and not to the resistor #81; (b) if it is a replacement for cap #75, it should be positive-grounded to the chassis.
I am assuming that the bottom-most tap on the voltage divider resistor #81 is not grounded (because is is offset by a fiber/felt washer).
4. Is the string of resisitors (#81-84 and #91) what creates the voltage drop from 400 v at the transformer to 50 v at cap #75?
Finally, bakelite cap #86 (nominally 0.3 uF per the schematic) appears to be made in internally of two 0.15 caps that are wired in parallel by a jumper between the end terminal and the middle terminal, correct?
5. If I want to use two caps instead of a single 0.3 uF as a replacement (i.e., keeping the jumper and the outward appearance), which terminal has the common end of the two caps? It seems that it should be terminal nearest the mounting lug (i.e., the one without the jumper from the end terminal), but can anyone confirm this?
I want to retain the original appearance as much as possible but will probably use a terminal strip for #87 and #88 until I can find replacement cans to restful and mount (is that what Kutztown is for?). Happy to post pics/notes when this phase is done.
This site is a fabulous resource!!!
Cheers and Happy New Year,
Matthew W. Woodruff
The attached pic shows the current situation.
Green arrow points to the lead from the center tap of the power transformer. This is 400 volts, correct?
My understanding is that this goes to the two cans at the rear and then to #75 (10 uF, 50v).
1. Does this lead go to the center terminal of the cans or to the outside? For all three cans? Or is the wiring reversed for #75 (pos. chassis ground)? Are there jumpers to make the connection (in an original set)?
White arrow points to two leads running from two side tabs on bakelite cap. #86. One has a terminal (not shown); the other appears to have been cut.
2. Same question as above: In an original set do these go to the center terminal of the cans or to the case? What is the polarity? (Positive? Because the center tap on the xfrm is negative?)
3. Since the cans are supposed to be insulated from the chassis, I assume that this is the reason that the neg. chassis ground on #87 & #88 does not short with the positive chassis ground on #75 -- or am I all wet?
Red arrow points to a cap (value unknown) that appears to have been retrofitted at some point in the past. This appears to be wrong for a number of reasons: (a) it does not conform to any part of the schematic for #87 or #88, which are connected to the center tap of the transformer and not to the resistor #81; (b) if it is a replacement for cap #75, it should be positive-grounded to the chassis.
I am assuming that the bottom-most tap on the voltage divider resistor #81 is not grounded (because is is offset by a fiber/felt washer).
4. Is the string of resisitors (#81-84 and #91) what creates the voltage drop from 400 v at the transformer to 50 v at cap #75?
Finally, bakelite cap #86 (nominally 0.3 uF per the schematic) appears to be made in internally of two 0.15 caps that are wired in parallel by a jumper between the end terminal and the middle terminal, correct?
5. If I want to use two caps instead of a single 0.3 uF as a replacement (i.e., keeping the jumper and the outward appearance), which terminal has the common end of the two caps? It seems that it should be terminal nearest the mounting lug (i.e., the one without the jumper from the end terminal), but can anyone confirm this?
I want to retain the original appearance as much as possible but will probably use a terminal strip for #87 and #88 until I can find replacement cans to restful and mount (is that what Kutztown is for?). Happy to post pics/notes when this phase is done.
This site is a fabulous resource!!!
Cheers and Happy New Year,
Matthew W. Woodruff
