The cap, labeled 350pF, came out of a E.H. Scott receiver, c. 1934. It had somehow dropped in value from 350 to 135pF, but showed no leakage. The cross-section exposed by my saw cut did not reveal any deformity, swelling, or other reason for the drop in value. The bakelite case seemed intact.
I didn't think that all Micamold condensers were paper. I know someone said that most are, but in my experience, most are mica insulated. In my television receiver, where all were paper (and leaky), they all had three dots, or, well, a 4th dot in the corner, which was either brown or white...can't remember. I'm looking at a removed one now, which I removed most of the paint on, and I see traces of a light brown or yellow (I'm going to eventually use it to make a mold).
So, at any rate, I guess you can find micas or papers all over the place. Anything is possible. It is probable that if they all test out fine, that you have micas. It is rare, at least in my case, to find paper condensers without leakage. It would be interesting to find out if there was a certain period that papers were used in place of micas, or if both were always available in mass quantity (and used in mass quantity). Again, I usually find micas in my radios (or at least mica looking condensers that check with absolutely no leakage what-so-ever, something I find hard to believe if they were paper units).
T.
A mica cap is made from sheets of mica with metal between them. The metal is attached on one end to a lead. If one layer of the foil doesn't make contact with a lead capacity will be reduced.
Norm
:I cut a Micamold 3-dot cap in two with a hack saw. It had mica dielectric, not paper.
:
:The cap, labeled 350pF, came out of a E.H. Scott receiver, c. 1934. It had somehow dropped in value from 350 to 135pF, but showed no leakage. The cross-section exposed by my saw cut did not reveal any deformity, swelling, or other reason for the drop in value. The bakelite case seemed intact.
The mica is unmistakable - certainly not paper.
I wish there was some way to tell for sure whether any given Micamold is paper or mica - besides cutting them apart. My operating theory is that any Micamold without leakage may be assumed to be mica.
This particular Micamold was in the BFO ckt, which is not critical for operation of the radio. It's conceivable that the cap was originally of a low value (135 instead of 350pF). But I don't see how the BFO could have worked in the factory, unless maybe the 50-pF adjustable cap it's in parallel with was tightened very, very tight. I also can't imagine that the set would have gotten out of the E.H. Scott factory without the BFO operation being checked.
Well, anyway, the BFO is working fine now.
:Hi Doug
:
: A mica cap is made from sheets of mica with metal between them. The metal is attached on one end to a lead. If one layer of the foil doesn't make contact with a lead capacity will be reduced.
:
:Norm
:
::I cut a Micamold 3-dot cap in two with a hack saw. It had mica dielectric, not paper.
::
::The cap, labeled 350pF, came out of a E.H. Scott receiver, c. 1934. It had somehow dropped in value from 350 to 135pF, but showed no leakage. The cross-section exposed by my saw cut did not reveal any deformity, swelling, or other reason for the drop in value. The bakelite case seemed intact.
marv
:I took one of the halves of the cap, and beveled back the saw-cut edge on my bench grinder. The cap looks to be two plates separated by one sheet of mica.
:
:The mica is unmistakable - certainly not paper.
:
:I wish there was some way to tell for sure whether any given Micamold is paper or mica - besides cutting them apart. My operating theory is that any Micamold without leakage may be assumed to be mica.
:
:This particular Micamold was in the BFO ckt, which is not critical for operation of the radio. It's conceivable that the cap was originally of a low value (135 instead of 350pF). But I don't see how the BFO could have worked in the factory, unless maybe the 50-pF adjustable cap it's in parallel with was tightened very, very tight. I also can't imagine that the set would have gotten out of the E.H. Scott factory without the BFO operation being checked.
:
:Well, anyway, the BFO is working fine now.
:
:
::Hi Doug
::
:: A mica cap is made from sheets of mica with metal between them. The metal is attached on one end to a lead. If one layer of the foil doesn't make contact with a lead capacity will be reduced.
::
::Norm
::
:::I cut a Micamold 3-dot cap in two with a hack saw. It had mica dielectric, not paper.
:::
:::The cap, labeled 350pF, came out of a E.H. Scott receiver, c. 1934. It had somehow dropped in value from 350 to 135pF, but showed no leakage. The cross-section exposed by my saw cut did not reveal any deformity, swelling, or other reason for the drop in value. The bakelite case seemed intact.
:The brown Micamolds in this RCA set have 3 or 6 (3 on each side) recessed dot spots, but only 1 spot is painted brown, and a gold spot just below in a non-recessed area. Both have "TYPE O" stamped into the cases. So whether paper, mica, 6/3 dots, they're all type O, but I'll be replacing all except transformers with new mica parts. The mire gets deeper!!
:
:marv
:
::I took one of the halves of the cap, and beveled back the saw-cut edge on my bench grinder. The cap looks to be two plates separated by one sheet of mica.
::
::The mica is unmistakable - certainly not paper.
::
::I wish there was some way to tell for sure whether any given Micamold is paper or mica - besides cutting them apart. My operating theory is that any Micamold without leakage may be assumed to be mica.
::
::This particular Micamold was in the BFO ckt, which is not critical for operation of the radio. It's conceivable that the cap was originally of a low value (135 instead of 350pF). But I don't see how the BFO could have worked in the factory, unless maybe the 50-pF adjustable cap it's in parallel with was tightened very, very tight. I also can't imagine that the set would have gotten out of the E.H. Scott factory without the BFO operation being checked.
::
::Well, anyway, the BFO is working fine now.
::
::
:::Hi Doug
:::
::: A mica cap is made from sheets of mica with metal between them. The metal is attached on one end to a lead. If one layer of the foil doesn't make contact with a lead capacity will be reduced.
:::
:::Norm
:::
::::I cut a Micamold 3-dot cap in two with a hack saw. It had mica dielectric, not paper.
::::
::::The cap, labeled 350pF, came out of a E.H. Scott receiver, c. 1934. It had somehow dropped in value from 350 to 135pF, but showed no leakage. The cross-section exposed by my saw cut did not reveal any deformity, swelling, or other reason for the drop in value. The bakelite case seemed intact.
:Marv, also a black dot in first position indicates a JAN spec mica. The four dot Micamold type have a black body and they are paper. Any six dot capacitor with first dot being silver is mica. Tho I mention I replace 3-dot and 4-dot Micamold caps I don't recall a 3-dot by Micamold being paper. They do have some three dot RESISTORS which look like capacitors. Some say resistor on the back, others don't. Your caps Marv are just what makes these dot type a pain...some dots the color has flaked off. You have to flip your cap over to read them. Your gold dot is the center dot on reverse side and is tolerance. Some companies stamped on the value along with colored dots and then some companies started marking them without the colored dots. Doug, to expand on what Norm said, the foil and mica sheets are alternated. One lead then connects to every other foil sheet and the other lead connects to the others. And for sure, you get a break and the capacity will change. I looked at the Micamold pat. no. 1973039, interesting.
:Bill VA
:
::The brown Micamolds in this RCA set have 3 or 6 (3 on each side) recessed dot spots, but only 1 spot is painted brown, and a gold spot just below in a non-recessed area. Both have "TYPE O" stamped into the cases. So whether paper, mica, 6/3 dots, they're all type O, but I'll be replacing all except transformers with new mica parts. The mire gets deeper!!
::
::marv
::
:::I took one of the halves of the cap, and beveled back the saw-cut edge on my bench grinder. The cap looks to be two plates separated by one sheet of mica.
:::
:::The mica is unmistakable - certainly not paper.
:::
:::I wish there was some way to tell for sure whether any given Micamold is paper or mica - besides cutting them apart. My operating theory is that any Micamold without leakage may be assumed to be mica.
:::
:::This particular Micamold was in the BFO ckt, which is not critical for operation of the radio. It's conceivable that the cap was originally of a low value (135 instead of 350pF). But I don't see how the BFO could have worked in the factory, unless maybe the 50-pF adjustable cap it's in parallel with was tightened very, very tight. I also can't imagine that the set would have gotten out of the E.H. Scott factory without the BFO operation being checked.
:::
:::Well, anyway, the BFO is working fine now.
:::
:::
::::Hi Doug
::::
:::: A mica cap is made from sheets of mica with metal between them. The metal is attached on one end to a lead. If one layer of the foil doesn't make contact with a lead capacity will be reduced.
::::
::::Norm
::::
:::::I cut a Micamold 3-dot cap in two with a hack saw. It had mica dielectric, not paper.
:::::
:::::The cap, labeled 350pF, came out of a E.H. Scott receiver, c. 1934. It had somehow dropped in value from 350 to 135pF, but showed no leakage. The cross-section exposed by my saw cut did not reveal any deformity, swelling, or other reason for the drop in value. The bakelite case seemed intact.
marv
:Marv, also a black dot in first position indicates a JAN spec mica. The four dot Micamold type have a black body and they are paper. Any six dot capacitor with first dot being silver is mica. Tho I mention I replace 3-dot and 4-dot Micamold caps I don't recall a 3-dot by Micamold being paper. They do have some three dot RESISTORS which look like capacitors. Some say resistor on the back, others don't. Your caps Marv are just what makes these dot type a pain...some dots the color has flaked off. You have to flip your cap over to read them. Your gold dot is the center dot on reverse side and is tolerance. Some companies stamped on the value along with colored dots and then some companies started marking them without the colored dots. Doug, to expand on what Norm said, the foil and mica sheets are alternated. One lead then connects to every other foil sheet and the other lead connects to the others. And for sure, you get a break and the capacity will change. I looked at the Micamold pat. no. 1973039, interesting.
:Bill VA
:
::The brown Micamolds in this RCA set have 3 or 6 (3 on each side) recessed dot spots, but only 1 spot is painted brown, and a gold spot just below in a non-recessed area. Both have "TYPE O" stamped into the cases. So whether paper, mica, 6/3 dots, they're all type O, but I'll be replacing all except transformers with new mica parts. The mire gets deeper!!
::
::marv
::
:::I took one of the halves of the cap, and beveled back the saw-cut edge on my bench grinder. The cap looks to be two plates separated by one sheet of mica.
:::
:::The mica is unmistakable - certainly not paper.
:::
:::I wish there was some way to tell for sure whether any given Micamold is paper or mica - besides cutting them apart. My operating theory is that any Micamold without leakage may be assumed to be mica.
:::
:::This particular Micamold was in the BFO ckt, which is not critical for operation of the radio. It's conceivable that the cap was originally of a low value (135 instead of 350pF). But I don't see how the BFO could have worked in the factory, unless maybe the 50-pF adjustable cap it's in parallel with was tightened very, very tight. I also can't imagine that the set would have gotten out of the E.H. Scott factory without the BFO operation being checked.
:::
:::Well, anyway, the BFO is working fine now.
:::
:::
::::Hi Doug
::::
:::: A mica cap is made from sheets of mica with metal between them. The metal is attached on one end to a lead. If one layer of the foil doesn't make contact with a lead capacity will be reduced.
::::
::::Norm
::::
:::::I cut a Micamold 3-dot cap in two with a hack saw. It had mica dielectric, not paper.
:::::
:::::The cap, labeled 350pF, came out of a E.H. Scott receiver, c. 1934. It had somehow dropped in value from 350 to 135pF, but showed no leakage. The cross-section exposed by my saw cut did not reveal any deformity, swelling, or other reason for the drop in value. The bakelite case seemed intact.
http://www.auction-image.com/is.php?i=9825&img=CAPACITOR_MICAM.jpg
http://www.auction-image.com/is.php?i=9826&img=CAP_MICA_KEEP_J.jpg
http://www.auction-image.com/is.php?i=9827&img=CAP_MICA_2_JPEG.jpg
http://www.auction-image.com/is.php?i=9828&img=RESISTORS_MICAM.jpg
http://www.auction-image.com/is.php?i=9829&img=MICAMOLD_MICA_3.jpg
Bill VA
:Bill,
:Even though there were 3/6 recessed positions, only the first was colored. The gold dot, which I assume to be 5% tolerance, was not in a recessed dot spot. The other with only 3 dots on one side was the same, and the back side was completely recessed with no markings except "Type O"
:
:marv
:
::Marv, also a black dot in first position indicates a JAN spec mica. The four dot Micamold type have a black body and they are paper. Any six dot capacitor with first dot being silver is mica. Tho I mention I replace 3-dot and 4-dot Micamold caps I don't recall a 3-dot by Micamold being paper. They do have some three dot RESISTORS which look like capacitors. Some say resistor on the back, others don't. Your caps Marv are just what makes these dot type a pain...some dots the color has flaked off. You have to flip your cap over to read them. Your gold dot is the center dot on reverse side and is tolerance. Some companies stamped on the value along with colored dots and then some companies started marking them without the colored dots. Doug, to expand on what Norm said, the foil and mica sheets are alternated. One lead then connects to every other foil sheet and the other lead connects to the others. And for sure, you get a break and the capacity will change. I looked at the Micamold pat. no. 1973039, interesting.
::Bill VA
::
:::The brown Micamolds in this RCA set have 3 or 6 (3 on each side) recessed dot spots, but only 1 spot is painted brown, and a gold spot just below in a non-recessed area. Both have "TYPE O" stamped into the cases. So whether paper, mica, 6/3 dots, they're all type O, but I'll be replacing all except transformers with new mica parts. The mire gets deeper!!
:::
:::marv
:::
::::I took one of the halves of the cap, and beveled back the saw-cut edge on my bench grinder. The cap looks to be two plates separated by one sheet of mica.
::::
::::The mica is unmistakable - certainly not paper.
::::
::::I wish there was some way to tell for sure whether any given Micamold is paper or mica - besides cutting them apart. My operating theory is that any Micamold without leakage may be assumed to be mica.
::::
::::This particular Micamold was in the BFO ckt, which is not critical for operation of the radio. It's conceivable that the cap was originally of a low value (135 instead of 350pF). But I don't see how the BFO could have worked in the factory, unless maybe the 50-pF adjustable cap it's in parallel with was tightened very, very tight. I also can't imagine that the set would have gotten out of the E.H. Scott factory without the BFO operation being checked.
::::
::::Well, anyway, the BFO is working fine now.
::::
::::
:::::Hi Doug
:::::
::::: A mica cap is made from sheets of mica with metal between them. The metal is attached on one end to a lead. If one layer of the foil doesn't make contact with a lead capacity will be reduced.
:::::
:::::Norm
:::::
::::::I cut a Micamold 3-dot cap in two with a hack saw. It had mica dielectric, not paper.
::::::
::::::The cap, labeled 350pF, came out of a E.H. Scott receiver, c. 1934. It had somehow dropped in value from 350 to 135pF, but showed no leakage. The cross-section exposed by my saw cut did not reveal any deformity, swelling, or other reason for the drop in value. The bakelite case seemed intact.
marv
:I got it now Marv. I thought you were talking about the three dots on one side and 3 dots on other side. Let me go over what I know about the flat type molded capacitors. Any six-dot with a white or black dot in first position is a MICA type. Any six-dot with a silver dot in the first position is a PAPER type. Any black body four-dot is a PAPER. Any other dot arrangement/body color is MICA as far as I know. I have not seen any other flat molded PAPER caps except as noted. Your Micamold type O is MICA. Why the splash of gold? I've seen silver and gold appear just about anywhere. Companies did provide tighter tolerance on request. Your 3-dot would be considered 20% rated at 500 wvdc. Here's some links:
:
: http://www.auction-image.com/is.php?i=9825&img=CAPACITOR_MICAM.jpg
:
:http://www.auction-image.com/is.php?i=9826&img=CAP_MICA_KEEP_J.jpg
:
:http://www.auction-image.com/is.php?i=9827&img=CAP_MICA_2_JPEG.jpg
:
:http://www.auction-image.com/is.php?i=9828&img=RESISTORS_MICAM.jpg
:
:http://www.auction-image.com/is.php?i=9829&img=MICAMOLD_MICA_3.jpg
:
:Bill VA
:
::Bill,
::Even though there were 3/6 recessed positions, only the first was colored. The gold dot, which I assume to be 5% tolerance, was not in a recessed dot spot. The other with only 3 dots on one side was the same, and the back side was completely recessed with no markings except "Type O"
::
::marv
::
:::Marv, also a black dot in first position indicates a JAN spec mica. The four dot Micamold type have a black body and they are paper. Any six dot capacitor with first dot being silver is mica. Tho I mention I replace 3-dot and 4-dot Micamold caps I don't recall a 3-dot by Micamold being paper. They do have some three dot RESISTORS which look like capacitors. Some say resistor on the back, others don't. Your caps Marv are just what makes these dot type a pain...some dots the color has flaked off. You have to flip your cap over to read them. Your gold dot is the center dot on reverse side and is tolerance. Some companies stamped on the value along with colored dots and then some companies started marking them without the colored dots. Doug, to expand on what Norm said, the foil and mica sheets are alternated. One lead then connects to every other foil sheet and the other lead connects to the others. And for sure, you get a break and the capacity will change. I looked at the Micamold pat. no. 1973039, interesting.
:::Bill VA
:::
::::The brown Micamolds in this RCA set have 3 or 6 (3 on each side) recessed dot spots, but only 1 spot is painted brown, and a gold spot just below in a non-recessed area. Both have "TYPE O" stamped into the cases. So whether paper, mica, 6/3 dots, they're all type O, but I'll be replacing all except transformers with new mica parts. The mire gets deeper!!
::::
::::marv
::::
:::::I took one of the halves of the cap, and beveled back the saw-cut edge on my bench grinder. The cap looks to be two plates separated by one sheet of mica.
:::::
:::::The mica is unmistakable - certainly not paper.
:::::
:::::I wish there was some way to tell for sure whether any given Micamold is paper or mica - besides cutting them apart. My operating theory is that any Micamold without leakage may be assumed to be mica.
:::::
:::::This particular Micamold was in the BFO ckt, which is not critical for operation of the radio. It's conceivable that the cap was originally of a low value (135 instead of 350pF). But I don't see how the BFO could have worked in the factory, unless maybe the 50-pF adjustable cap it's in parallel with was tightened very, very tight. I also can't imagine that the set would have gotten out of the E.H. Scott factory without the BFO operation being checked.
:::::
:::::Well, anyway, the BFO is working fine now.
:::::
:::::
::::::Hi Doug
::::::
:::::: A mica cap is made from sheets of mica with metal between them. The metal is attached on one end to a lead. If one layer of the foil doesn't make contact with a lead capacity will be reduced.
::::::
::::::Norm
::::::
:::::::I cut a Micamold 3-dot cap in two with a hack saw. It had mica dielectric, not paper.
:::::::
:::::::The cap, labeled 350pF, came out of a E.H. Scott receiver, c. 1934. It had somehow dropped in value from 350 to 135pF, but showed no leakage. The cross-section exposed by my saw cut did not reveal any deformity, swelling, or other reason for the drop in value. The bakelite case seemed intact.
I can easily accept resistor color coding bands... that's really fine no problem. A standard there. ( Even the older Body-End-Dot stuff)
.. but caps stink..!!!
Even todays modern film caps where they have all the opportubity in the world to print te ACTUAL value... they don't!
Why print 103K ?? ... when for the same effort you can easily simply print .01uf
I don't like to have to translate EVERYthing all the darned time... arggggg
marv
Bill,
:Thanks for the pix. Except for one condenser, all my molded types look like the last .jpg, but only 1 dot is painted. Even the 6 dot version has only one dot painted. Unexpectedly all the (may be) micas appear bad, but a long red/org part (720mmf), which I was assured is mica, tested well. The parts list doesn't include reference designators, and only a single 100mmf is called mica, while other 100mmf are not. This set, RCA 16T2 has obviously been in a shop, but don't know the era it came from or its history. I've only found 5 good condensers (the 720mmf and 4 micas inside IF cans)) in the entire set, and most of the wiring has deteriorated beyond usability. Have ordered molded mica for everything that was molded. Can hardly wait for my parts from PTOP, finish and fire it up.
:
:marv
:
::I got it now Marv. I thought you were talking about the three dots on one side and 3 dots on other side. Let me go over what I know about the flat type molded capacitors. Any six-dot with a white or black dot in first position is a MICA type. Any six-dot with a silver dot in the first position is a PAPER type. Any black body four-dot is a PAPER. Any other dot arrangement/body color is MICA as far as I know. I have not seen any other flat molded PAPER caps except as noted. Your Micamold type O is MICA. Why the splash of gold? I've seen silver and gold appear just about anywhere. Companies did provide tighter tolerance on request. Your 3-dot would be considered 20% rated at 500 wvdc. Here's some links:
::
:: http://www.auction-image.com/is.php?i=9825&img=CAPACITOR_MICAM.jpg
::
::http://www.auction-image.com/is.php?i=9826&img=CAP_MICA_KEEP_J.jpg
::
::http://www.auction-image.com/is.php?i=9827&img=CAP_MICA_2_JPEG.jpg
::
::http://www.auction-image.com/is.php?i=9828&img=RESISTORS_MICAM.jpg
::
::http://www.auction-image.com/is.php?i=9829&img=MICAMOLD_MICA_3.jpg
::
::Bill VA
::
:::Bill,
:::Even though there were 3/6 recessed positions, only the first was colored. The gold dot, which I assume to be 5% tolerance, was not in a recessed dot spot. The other with only 3 dots on one side was the same, and the back side was completely recessed with no markings except "Type O"
:::
:::marv
:::
::::Marv, also a black dot in first position indicates a JAN spec mica. The four dot Micamold type have a black body and they are paper. Any six dot capacitor with first dot being silver is mica. Tho I mention I replace 3-dot and 4-dot Micamold caps I don't recall a 3-dot by Micamold being paper. They do have some three dot RESISTORS which look like capacitors. Some say resistor on the back, others don't. Your caps Marv are just what makes these dot type a pain...some dots the color has flaked off. You have to flip your cap over to read them. Your gold dot is the center dot on reverse side and is tolerance. Some companies stamped on the value along with colored dots and then some companies started marking them without the colored dots. Doug, to expand on what Norm said, the foil and mica sheets are alternated. One lead then connects to every other foil sheet and the other lead connects to the others. And for sure, you get a break and the capacity will change. I looked at the Micamold pat. no. 1973039, interesting.
::::Bill VA
::::
:::::The brown Micamolds in this RCA set have 3 or 6 (3 on each side) recessed dot spots, but only 1 spot is painted brown, and a gold spot just below in a non-recessed area. Both have "TYPE O" stamped into the cases. So whether paper, mica, 6/3 dots, they're all type O, but I'll be replacing all except transformers with new mica parts. The mire gets deeper!!
:::::
:::::marv
:::::
::::::I took one of the halves of the cap, and beveled back the saw-cut edge on my bench grinder. The cap looks to be two plates separated by one sheet of mica.
::::::
::::::The mica is unmistakable - certainly not paper.
::::::
::::::I wish there was some way to tell for sure whether any given Micamold is paper or mica - besides cutting them apart. My operating theory is that any Micamold without leakage may be assumed to be mica.
::::::
::::::This particular Micamold was in the BFO ckt, which is not critical for operation of the radio. It's conceivable that the cap was originally of a low value (135 instead of 350pF). But I don't see how the BFO could have worked in the factory, unless maybe the 50-pF adjustable cap it's in parallel with was tightened very, very tight. I also can't imagine that the set would have gotten out of the E.H. Scott factory without the BFO operation being checked.
::::::
::::::Well, anyway, the BFO is working fine now.
::::::
::::::
:::::::Hi Doug
:::::::
::::::: A mica cap is made from sheets of mica with metal between them. The metal is attached on one end to a lead. If one layer of the foil doesn't make contact with a lead capacity will be reduced.
:::::::
:::::::Norm
:::::::
::::::::I cut a Micamold 3-dot cap in two with a hack saw. It had mica dielectric, not paper.
::::::::
::::::::The cap, labeled 350pF, came out of a E.H. Scott receiver, c. 1934. It had somehow dropped in value from 350 to 135pF, but showed no leakage. The cross-section exposed by my saw cut did not reveal any deformity, swelling, or other reason for the drop in value. The bakelite case seemed intact.
Bill VA
:Peter,
:I'm sure it all started as a gimmick to improve the bottom line, by introducing a little secrecy/coding and added compettition. It may have also coincided with the switch to our version of the metric system, another joke as far as I'm concerned. Inches, feet and miles made us the greatest economic power on earth, so why did we need to switch.
:
:marv
:
:
:Bill,
::Thanks for the pix. Except for one condenser, all my molded types look like the last .jpg, but only 1 dot is painted. Even the 6 dot version has only one dot painted. Unexpectedly all the (may be) micas appear bad, but a long red/org part (720mmf), which I was assured is mica, tested well. The parts list doesn't include reference designators, and only a single 100mmf is called mica, while other 100mmf are not. This set, RCA 16T2 has obviously been in a shop, but don't know the era it came from or its history. I've only found 5 good condensers (the 720mmf and 4 micas inside IF cans)) in the entire set, and most of the wiring has deteriorated beyond usability. Have ordered molded mica for everything that was molded. Can hardly wait for my parts from PTOP, finish and fire it up.
::
::marv
::
:::I got it now Marv. I thought you were talking about the three dots on one side and 3 dots on other side. Let me go over what I know about the flat type molded capacitors. Any six-dot with a white or black dot in first position is a MICA type. Any six-dot with a silver dot in the first position is a PAPER type. Any black body four-dot is a PAPER. Any other dot arrangement/body color is MICA as far as I know. I have not seen any other flat molded PAPER caps except as noted. Your Micamold type O is MICA. Why the splash of gold? I've seen silver and gold appear just about anywhere. Companies did provide tighter tolerance on request. Your 3-dot would be considered 20% rated at 500 wvdc. Here's some links:
:::
::: http://www.auction-image.com/is.php?i=9825&img=CAPACITOR_MICAM.jpg
:::
:::http://www.auction-image.com/is.php?i=9826&img=CAP_MICA_KEEP_J.jpg
:::
:::http://www.auction-image.com/is.php?i=9827&img=CAP_MICA_2_JPEG.jpg
:::
:::http://www.auction-image.com/is.php?i=9828&img=RESISTORS_MICAM.jpg
:::
:::http://www.auction-image.com/is.php?i=9829&img=MICAMOLD_MICA_3.jpg
:::
:::Bill VA
:::
::::Bill,
::::Even though there were 3/6 recessed positions, only the first was colored. The gold dot, which I assume to be 5% tolerance, was not in a recessed dot spot. The other with only 3 dots on one side was the same, and the back side was completely recessed with no markings except "Type O"
::::
::::marv
::::
:::::Marv, also a black dot in first position indicates a JAN spec mica. The four dot Micamold type have a black body and they are paper. Any six dot capacitor with first dot being silver is mica. Tho I mention I replace 3-dot and 4-dot Micamold caps I don't recall a 3-dot by Micamold being paper. They do have some three dot RESISTORS which look like capacitors. Some say resistor on the back, others don't. Your caps Marv are just what makes these dot type a pain...some dots the color has flaked off. You have to flip your cap over to read them. Your gold dot is the center dot on reverse side and is tolerance. Some companies stamped on the value along with colored dots and then some companies started marking them without the colored dots. Doug, to expand on what Norm said, the foil and mica sheets are alternated. One lead then connects to every other foil sheet and the other lead connects to the others. And for sure, you get a break and the capacity will change. I looked at the Micamold pat. no. 1973039, interesting.
:::::Bill VA
:::::
::::::The brown Micamolds in this RCA set have 3 or 6 (3 on each side) recessed dot spots, but only 1 spot is painted brown, and a gold spot just below in a non-recessed area. Both have "TYPE O" stamped into the cases. So whether paper, mica, 6/3 dots, they're all type O, but I'll be replacing all except transformers with new mica parts. The mire gets deeper!!
::::::
::::::marv
::::::
:::::::I took one of the halves of the cap, and beveled back the saw-cut edge on my bench grinder. The cap looks to be two plates separated by one sheet of mica.
:::::::
:::::::The mica is unmistakable - certainly not paper.
:::::::
:::::::I wish there was some way to tell for sure whether any given Micamold is paper or mica - besides cutting them apart. My operating theory is that any Micamold without leakage may be assumed to be mica.
:::::::
:::::::This particular Micamold was in the BFO ckt, which is not critical for operation of the radio. It's conceivable that the cap was originally of a low value (135 instead of 350pF). But I don't see how the BFO could have worked in the factory, unless maybe the 50-pF adjustable cap it's in parallel with was tightened very, very tight. I also can't imagine that the set would have gotten out of the E.H. Scott factory without the BFO operation being checked.
:::::::
:::::::Well, anyway, the BFO is working fine now.
:::::::
:::::::
::::::::Hi Doug
::::::::
:::::::: A mica cap is made from sheets of mica with metal between them. The metal is attached on one end to a lead. If one layer of the foil doesn't make contact with a lead capacity will be reduced.
::::::::
::::::::Norm
::::::::
:::::::::I cut a Micamold 3-dot cap in two with a hack saw. It had mica dielectric, not paper.
:::::::::
:::::::::The cap, labeled 350pF, came out of a E.H. Scott receiver, c. 1934. It had somehow dropped in value from 350 to 135pF, but showed no leakage. The cross-section exposed by my saw cut did not reveal any deformity, swelling, or other reason for the drop in value. The bakelite case seemed intact.
T.
Bill VA
:Well, if there was any standardization like with most resistors, colors would help. Sometimes colors are easier to read than small numbers. Dot condensers do have some standardization, but there does seem to be a few systems in use...annoying. The coding on modern condensers is annoying, too. Some have actual MFD. Some have pF. Some have the code. Who knows... If you have a condenser with 103 or 221 on it, is it 220 pF or 221 pF? Is the 103 10000 pF or 103 pF? With some, it's obvious when the voltage is given, and there's a K or something else afterward...you know that it's a code. When it's just three numbers, though, who knows? Anyway, I'm complaining to the choir here.. should focus this on the manufacturers and the ASA.
:
:T.
Then, what is 100. Is it 10 pF or 100 pF??
T.
T.
http://www.auction-image.com/is.php?i=9992&img=CAPACITOR_MICA_.jpg
are the value as stamped. Depending on the type of your 100 it could be 10PF...or 100 PF. The most modern silvered mica of PF measurement I buy has the value, eg., 680, maybe the tolerance but no unit of measurement designation (PF). A capacitor such as the disc type with a decimal point like .0015 is measured in MF. With exceptions I would say the decimal point is identified most of the time with MF value types.
Bill VA
:Typically my 10 pF condensers just have 10 printed on them.
:
:T.
marv
:There's way too many variations today for me to keep up with. But an older mica such as these:
:
:http://www.auction-image.com/is.php?i=9992&img=CAPACITOR_MICA_.jpg
:
:are the value as stamped. Depending on the type of your 100 it could be 10PF...or 100 PF. The most modern silvered mica of PF measurement I buy has the value, eg., 680, maybe the tolerance but no unit of measurement designation (PF). A capacitor such as the disc type with a decimal point like .0015 is measured in MF. With exceptions I would say the decimal point is identified most of the time with MF value types.
:
:Bill VA
:
::Typically my 10 pF condensers just have 10 printed on them.
::
::T.
Bill
:Bill,
:Got 2 like that in my set, a 180 and a 330, but they look so cheap, was sure they were paper. I did order mica to replace them though, which I thought was a safe bet. Received my order from PTOP of several different values of molded mica, and they look like the old style with 6 dots. Still can't read the dots to get the stated/measured value. Even stranger, when I cleaned the leads of years of crud, underneath the solder tinning appears to be brass wire leads vs copper. Now that really is a first for me.
:
:marv
:
::There's way too many variations today for me to keep up with. But an older mica such as these:
::
::http://www.auction-image.com/is.php?i=9992&img=CAPACITOR_MICA_.jpg
::
::are the value as stamped. Depending on the type of your 100 it could be 10PF...or 100 PF. The most modern silvered mica of PF measurement I buy has the value, eg., 680, maybe the tolerance but no unit of measurement designation (PF). A capacitor such as the disc type with a decimal point like .0015 is measured in MF. With exceptions I would say the decimal point is identified most of the time with MF value types.
::
::Bill VA
::
:::Typically my 10 pF condensers just have 10 printed on them.
:::
:::T.
marv
:Marv, what's the brand? I hope you got the 6-dot with first position dot being white or black. I don't know about brass leads. For the most I believe the leads are tinned copper. I'll send you something so you can read the 6-dot caps.
:
:Bill
:
:
:
::Bill,
::Got 2 like that in my set, a 180 and a 330, but they look so cheap, was sure they were paper. I did order mica to replace them though, which I thought was a safe bet. Received my order from PTOP of several different values of molded mica, and they look like the old style with 6 dots. Still can't read the dots to get the stated/measured value. Even stranger, when I cleaned the leads of years of crud, underneath the solder tinning appears to be brass wire leads vs copper. Now that really is a first for me.
::
::marv
::
:::There's way too many variations today for me to keep up with. But an older mica such as these:
:::
:::http://www.auction-image.com/is.php?i=9992&img=CAPACITOR_MICA_.jpg
:::
:::are the value as stamped. Depending on the type of your 100 it could be 10PF...or 100 PF. The most modern silvered mica of PF measurement I buy has the value, eg., 680, maybe the tolerance but no unit of measurement designation (PF). A capacitor such as the disc type with a decimal point like .0015 is measured in MF. With exceptions I would say the decimal point is identified most of the time with MF value types.
:::
:::Bill VA
:::
::::Typically my 10 pF condensers just have 10 printed on them.
::::
::::T.
T.
http://www.auction-image.com/is.php?i=10001&img=CAP_TO_MICA_JPE.jpg
I only have a few left as samples. I normally toss out all parts which have been replaced. So maybe some others can crack open some. We can resolve this. Perhaps same molding, different times involved, maybe both.
Bill VA
:Those "cheap" ones you see in your set, and that Bill shows as mica, are indeed paper condensers. I cracked some open. That's why they're leaky. They were all over my V170.
:
:T.
Bill VA
:Thomas, cracked two. Clearly mica. No paper.
:
:http://www.auction-image.com/is.php?i=10001&img=CAP_TO_MICA_JPE.jpg
:
:I only have a few left as samples. I normally toss out all parts which have been replaced. So maybe some others can crack open some. We can resolve this. Perhaps same molding, different times involved, maybe both.
:
:Bill VA
:
::Those "cheap" ones you see in your set, and that Bill shows as mica, are indeed paper condensers. I cracked some open. That's why they're leaky. They were all over my V170.
::
::T.
T.
The other is read the same except the gold is a multiplier of .1 making that cap a 10 mmf. So I don't know about that one if you measured 100 mmf. And it's a type 5 and these do have tinned brass wire. I see more so now why I replace the flat molded ones with dipped silver mica. Post an e-mail so I can send the chart I have. Not sure it will help if you have mixed up color dots. Just measure them and act accordingly.
Bill
:Bill,
:Some are ERIE, the red body and reading with the arrow top row left to right Brn, blk, blk, bottom row right to left, blk, silver, grn and measure 100mmf. Cornell-Dublier red body Type "S" or "5", top row with arrow left to right, brn, blk, blk, bottom row right to left, gold, silver, grn, and measure 100mmf
:I can't correlate any of this color code to 100mmf.
:Don't know about the others of which there are 120, 180, 330, 680 and 820mmf.
:
:marv
:
::Marv, what's the brand? I hope you got the 6-dot with first position dot being white or black. I don't know about brass leads. For the most I believe the leads are tinned copper. I'll send you something so you can read the 6-dot caps.
::
::Bill
::
::
::
:::Bill,
:::Got 2 like that in my set, a 180 and a 330, but they look so cheap, was sure they were paper. I did order mica to replace them though, which I thought was a safe bet. Received my order from PTOP of several different values of molded mica, and they look like the old style with 6 dots. Still can't read the dots to get the stated/measured value. Even stranger, when I cleaned the leads of years of crud, underneath the solder tinning appears to be brass wire leads vs copper. Now that really is a first for me.
:::
:::marv
:::
::::There's way too many variations today for me to keep up with. But an older mica such as these:
::::
::::http://www.auction-image.com/is.php?i=9992&img=CAPACITOR_MICA_.jpg
::::
::::are the value as stamped. Depending on the type of your 100 it could be 10PF...or 100 PF. The most modern silvered mica of PF measurement I buy has the value, eg., 680, maybe the tolerance but no unit of measurement designation (PF). A capacitor such as the disc type with a decimal point like .0015 is measured in MF. With exceptions I would say the decimal point is identified most of the time with MF value types.
::::
::::Bill VA
::::
:::::Typically my 10 pF condensers just have 10 printed on them.
:::::
:::::T.
marv
:Marv, the brown (1), black (0), black (0) equals 100. Then reading bottom row right to left, black (0)and the multiplier is 1. 100 x 1 = 100 mmf. The silver dot is 10% tolerance, the green dot is 500 volts.
:
:The other is read the same except the gold is a multiplier of .1 making that cap a 10 mmf. So I don't know about that one if you measured 100 mmf. And it's a type 5 and these do have tinned brass wire. I see more so now why I replace the flat molded ones with dipped silver mica. Post an e-mail so I can send the chart I have. Not sure it will help if you have mixed up color dots. Just measure them and act accordingly.
:
:Bill
:
::Bill,
::Some are ERIE, the red body and reading with the arrow top row left to right Brn, blk, blk, bottom row right to left, blk, silver, grn and measure 100mmf. Cornell-Dublier red body Type "S" or "5", top row with arrow left to right, brn, blk, blk, bottom row right to left, gold, silver, grn, and measure 100mmf
::I can't correlate any of this color code to 100mmf.
::Don't know about the others of which there are 120, 180, 330, 680 and 820mmf.
::
::marv
::
:::Marv, what's the brand? I hope you got the 6-dot with first position dot being white or black. I don't know about brass leads. For the most I believe the leads are tinned copper. I'll send you something so you can read the 6-dot caps.
:::
:::Bill
:::
:::
:::
::::Bill,
::::Got 2 like that in my set, a 180 and a 330, but they look so cheap, was sure they were paper. I did order mica to replace them though, which I thought was a safe bet. Received my order from PTOP of several different values of molded mica, and they look like the old style with 6 dots. Still can't read the dots to get the stated/measured value. Even stranger, when I cleaned the leads of years of crud, underneath the solder tinning appears to be brass wire leads vs copper. Now that really is a first for me.
::::
::::marv
::::
:::::There's way too many variations today for me to keep up with. But an older mica such as these:
:::::
:::::http://www.auction-image.com/is.php?i=9992&img=CAPACITOR_MICA_.jpg
:::::
:::::are the value as stamped. Depending on the type of your 100 it could be 10PF...or 100 PF. The most modern silvered mica of PF measurement I buy has the value, eg., 680, maybe the tolerance but no unit of measurement designation (PF). A capacitor such as the disc type with a decimal point like .0015 is measured in MF. With exceptions I would say the decimal point is identified most of the time with MF value types.
:::::
:::::Bill VA
:::::
::::::Typically my 10 pF condensers just have 10 printed on them.
::::::
::::::T.