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 Post subject: Philco radio model 620
PostPosted: Sep Sat 27, 2003 10:53 pm 
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I just received a philco radio model 620. i cleaned it up and changed the paper and electrolytic capacitors.The radio powers up and the tubes light. But i can not get any stations. i do get a low hum on two positions of the band coming out of the speaker. The hum sounds as though a station would pop up but as i turn the tuning condenser i get nothing. On the other position of the band i receive tone. like the sound you hear when you see color bars on a TV station or when the emergency broad cast system comes on your TV set.Can any one give me some suggestion of what to do next. Thank.<P>------------------<BR>


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 Post subject: Philco radio model 620
PostPosted: Sep Sat 27, 2003 11:21 pm 
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Carmine,<P>Check for open R.F. or oscillator or I.F. transformer coils in the front end. Most likely there is a break in one of them. Simple continuity checks will tell. Also check for proper voltages on plates and screen of tubes.<P>Philco coils are notorious for going open. Look for a green-ish corrosion near solder lugs and terminals on the coils.<P><P>------------------<BR>Chuck Schwark<BR>The Philco Repair Bench at<BR> <BR> <A HREF="http://www.philcorepairbench.com" TARGET=_blank>http://www.philcorepairbench.com</A>


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 Post subject: Philco radio model 620
PostPosted: Sep Sun 28, 2003 2:59 am 
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Hi chuck,<BR> Thanks for your suggestions.Im not that expierienced in restoring Philco radios or any other radios from The 30's and i might sound stupid but to check for continuity in the coils do i put the setting on the multimeter on DC voltage and place negative end to chassis and positive to the different pins? i guess if there is voltage that means its not opened.What does it mean if i get negative voltage readings on the coil pins?<BR>Im going to give it a shot. its a nice radio and i like to get it working. <BR> Thanks <P>------------------<BR>


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 Post subject: Philco radio model 620
PostPosted: Sep Sun 28, 2003 3:11 am 
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Hi Carmine,<P>One important point - before making any continuity measurements, make sure the radio is unplugged, and that it has been turned off for at least ten minutes, to allow the capacitors to discharge. Otherwise residual voltages in the circuit can throw off the readings, and could be dangerous.<P>To measure continuity you use the Ohms function on your meter. If the meter is auto-ranging there will be only one Ohms position for the switch; if manual there will be several, and you should select the 20,000-ohm range. The meter may use a Greek Omega Ω symbol rather than the word Ohms. With the test leads shorted together, you should read 0, or close to 0. With the leads open, the meter will indicate an open circuit, but the indication varies from one meter to another. Many meters display the letters OL.<P>You will need to identify the correct pins on the transformers. Philco schematics usually have a drawing of each RF transformer with numbers assigned to the pins, corresponding to the symbol on the schematic. For the tests that we're doing here, the Red and Black meter leads are interchangeable; it doesn't matter which one is connected to which transformer pin or lead.<P>IF transformers usually have color-coded leads. The primary would be the red and blue leads; the secondary is normally the black and green (or brown) leads. If you measure across the primary, you should read a low value, perhaps 100 to 1000 ohms; similarly across the secondary leads. If you measure from one primary lead to one secondary lead, you should not get a reading, just as though the meter leads were not connected to anything.<P>------------------<BR>73 de Leigh W3NLB


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 Post subject: Philco radio model 620
PostPosted: Sep Sun 28, 2003 8:11 am 
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Thank you Leigh i will try that in the morning and see what i get.<P>------------------<BR>


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 Post subject: Philco radio model 620
PostPosted: Sep Sun 28, 2003 3:45 pm 
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Hi Carmine,<P>I just got into the shop and pulled the schematic on the 620. It seems I was a bit high in my resistance estimates.<P>The IF transformers should read 12 ohms on both the primary and secondary windings. The RF and oscillator transformer windings are from 0.1 to 60 ohms, depending on which winding we're discussing. You should use the 200-ohm range on a manual-ranging DVM for these readings.<P>Unfortunately, the schematic does not give terminal diagrams for the transformers, so you'll have to trace out the circuit through the switches, or go directly from the tube pins.<P>------------------<BR>73 de Leigh W3NLB


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 Post subject: Philco radio model 620
PostPosted: Sep Sun 28, 2003 6:33 pm 
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Hi Carmine,<BR>The amount of ohm’s at this time is unimportant, all we are trying to find out is if transformer are open. <BR>Most meters have a continuity buzzer, yours may not. All Leigh is saying is if we have ohm’s on them, there not open. Like Chuck said, PHILCO’s are famous for open coils. Each terminal should have continuity to each other. The tube pins at THIS point are not important.<BR>There are a lot of things that could cause what your saying!! I notice that you say nothing about if the tube’s are OK, or if you have checked the resistors. There are 3 bakelite blocks in that and 3 flex resisters that need to be checked also. You say the paper capacitors were replaced , but what about the one’s in the blocks ??<P>And do you have a good schematic for it??<P>------------------<BR>Rick Dippolito<BR>THE PHILCO RESTORER at<BR> <A HREF="http://hometown.aol.com/philcorestorer/myhomepage/index.html" TARGET=_blank>http://hometown.aol.com/philcorestorer/myhomepage/index.html</A>


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 Post subject: Philco radio model 620
PostPosted: Sep Sun 28, 2003 11:17 pm 
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Hi guys<BR> First the tubes are good i checked them by putting them in an old emerson radio with the same tube numbers and they were all good except the 75 and i had agood one on hand.<BR> The block capacitor i did not change. there look like there are three. The numbers on the side of the blocks were 4989DG, 6287DU, 3793DG, and did could not find there values and when i did find sothing it was not the exact lettering that was on Chucks Web site .Great web site by the way. and schamatic was no help. i did the buzz test and the 6A7 i get nothing. if i put the tube shield over the 78 Tube i get nothing on that tube. When i removed the shield from the 78 tube and replaced the 78 tube with 6D6 i got a loud buzz from the grid of that tube. still nothing out of the 6A7 so now im up to what Leigh suggested (the continuity check) first thing i figure would be the transformer that has the grid cap and wire coming out of it going to the 6D6 or 78 tube. This transformer also has a wire going to the plate of the 6A7 and wire that goes to a tie down that works its way down to the nuber 4 pin of the 6D6 or 78. and one wire goes to one of the bigger transformers. so im going to test those connections with the power cord out of the wall. switch on the ON position stay tune.<BR> Thanks<P>------------------<BR>


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 Post subject: Philco radio model 620
PostPosted: Sep Mon 29, 2003 8:44 pm 
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Hi Leigh, how did you get the omega symbol to appear on the forum please?<BR>Don Black.<P>------------------<BR>


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 Post subject: Philco radio model 620
PostPosted: Sep Mon 29, 2003 9:45 pm 
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Hi Don -<P>It's a special HTML character - ampersand, pound, nine, three, seven, semicolon.<P>Ω<P>See a long list here: <A HREF="http://www.htmlhelp.com/reference/html40/entities/symbols.html" TARGET=_blank>http://www.htmlhelp.com/reference/html40/entities/symbols.html</A> <P>Kevin<P>------------------<BR>


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 Post subject: Philco radio model 620
PostPosted: Sep Mon 29, 2003 10:28 pm 
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Hi Don, Kevin,<P>Actually, it's simpler. I cheat <IMG SRC="http://antiqueradios.com/forums/smile.gif"><P>Just bring up MS Word, do an Insert / Symbol, select the desired symbol from the map and insert it into the document. Then highlight it in the document and do a Control-C to copy it to the clipboard. Go back to where you were and use Control-V to paste it where you want it.<P>Works with all of the symbols on the first symbol page. Haven't tried it with others... there are dozens of pages of symbols.<P>------------------<BR>73 de Leigh W3NLB


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 Post subject: Philco radio model 620
PostPosted: Sep Mon 29, 2003 10:46 pm 
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Hi Carmine,<P>The bakelite blocks that you mentioned each contain two paper capacitors, which should be changed out. There are different ways to do this, depending on who you ask. I prefer to remove the tar and the parts, put in new capacitors, and fill it up with hot-melt glue. (The last step is really not necessary.)<P>To accomplish this, you must disconnect any wires and components from the block, then remove the single screw holding it to the chassis. The blocks with the G suffix will have a metal tab that goes under the screw head, to ground one set of terminals on the block. The U suffix indicates an ungrounded block.<P>Once you have the block out of the radio, turn it over and you'll see that it's filled with black tar. I use an awl to dig it out; some people try to melt it, but it stinks <IMG SRC="http://antiqueradios.com/forums/frown.gif"> Be careful not to break the bakelite; it's rather thin.<P>When you get most of the tar out, you'll see that there are two capacitors inside, with leads going through holes up to the solder terminals. Remove them and replace them with new 630-volt plastic caps, just like you use elsewhere in the radio. The 4989 has two 0.10 mfd caps; the 6287 has two 0.15 mfd caps; and the 3793 has two 0.015 mfd caps. These are all standard modern values.<P>There's a good chart of these values on the Philco Repair Bench at <A HREF="http://www.philcorepairbench.com/bblokcap.htm" TARGET=_blank>http://www.philcorepairbench.com/bblokcap.htm</A> <P>There's also a tutorial on rebuilding the bakelite blocks on the same site at <A HREF="http://www.philcorepairbench.com/capbuild.htm" TARGET=_blank>http://www.philcorepairbench.com/capbuild.htm</A> , unfortunately no pix.<P>The bakelite blocks can be a bit complicated. Some of them contain resistors or mica caps as well as the paper caps. Exercise care when decanting these beasts to ensure that you don't break the contents <IMG SRC="http://antiqueradios.com/forums/smile.gif"><P><BR>------------------<BR>73 de Leigh W3NLB


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 Post subject: Philco radio model 620
PostPosted: Sep Tue 30, 2003 12:12 am 
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Leigh, one of the blocks in his set, number 39 in the schematic an 8035DG does have 2 - 110 Mica’s in it and not capacitors!!<BR>For a better article ( I think it is, but then I would ) on bakelites click on below :<BR> <A HREF="http://hometown.aol.com/philcorestorer/page8.html" TARGET=_blank>http://hometown.aol.com/philcorestorer/page8.html</A> <P><BR><P>------------------<BR>Rick Dippolito<BR>THE PHILCO RESTORER at<BR> <A HREF="http://hometown.aol.com/philcorestorer/myhomepage/index.html" TARGET=_blank>http://hometown.aol.com/philcorestorer/myhomepage/index.html</A>


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 Post subject: Philco radio model 620
PostPosted: Sep Tue 30, 2003 1:52 am 
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Hi Rick,<P>She didn't mention a number 8035. The three that she listed have only paper caps. <P>Perhaps there's a fourth one that she overlooked.<P>------------------<BR>73 de Leigh W3NLB


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 Post subject: Philco radio model 620
PostPosted: Sep Tue 30, 2003 6:37 am 
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Hi Guys<BR> I think that Rick is mistaken on the 4th Bakelite Block. according to my schematic part 39 for the model 620 is a mica capacitor .00011 Mfd. and nothing about this capacitor being a block capacitor. i dont see any block capacitor in that position.i would like to change those block capacitors and Leigh thanks for the info but im a little confused as to what pins on the bakelite blocks to attach the new capacitor to but i guess once i open them up like you said i'll see what lugs they are connected to. On the Philco Restorers web page chart it has pins for a resistor 2&3 with the 6287DU i guess ignore that there is no resistor in that block? Other questions maybe you can clear up for me . if i connect two condensers in parallel will that give me the sum of both of them together example: .05 mfd at 600 volts + .05 mfd at 600 volts = .10 at 1200 volts ? And can i use disk capacitors with the same or slightly higher values to replace the mica capacitors?<BR>Also getting back to my progress on the radio,i did a continuity check on the 2nd IF Transformer and its reading was infinity after taking it out and cleaning and sodering new leads to the primary wires and secondary wires, i got a continuity reading 11.7 ohms across the primary and 11.7 ohms across the secondary.When i put transformer back in the circuit i got the same reading. so now i think thats OK im going on to the next transformer and check that one out. i can see this will be no rush job. <BR> <P>------------------<BR>


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 Post subject: Philco radio model 620
PostPosted: Sep Tue 30, 2003 7:02 am 
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Hi Carmine,<P>Let me take these in reverse order (for no particular reason <IMG SRC="http://antiqueradios.com/forums/smile.gif">). The 2nd IF transformer sounds fine. 11.7 ohms is exactly what you should get. Well done on the repair!<P>Regarding capacitors in parallel: It follows the "weakest link" principle. If you have a bunch of 1,000-volt capacitors in parallel with one 100-volt cap, the voltage rating of the combination would be 100 volts. If you apply 200 volts, the 100-volt cap would fail, even though the others wouldn't care. The capacitance of a parallel combination is equal to the sum of the individual values.<P>Regarding mica v. disc ceramic caps: The usual problem is tolerance. Mica caps are very tight-tolerance parts, disc ceramics are not. This can make a difference in a tuned circuit. Micas are typically 5%, sometimes as tight as 1%. Disc ceramics are 10% at best. There's also a potential for thermal instability. The temperature characteristics of micas are more closely controlled than those of disc ceramics. <P>There is one type of ceramic cap that is a satisfactory substitute, it's called a tubular ceramic. It's a little white tube with paint dots on it, like a miniature dog-bone resistor. These are not made any more, but if you find some surplus, they are probably still good. Very fragile due to extremely thin ceramic wall.<P>Regarding part number 39: The capacitance values 110 mmfd and .00011 mfd are the same, so you are both talking about the same component. I would have to guess that Philco used the bakelite tub in some versions, but used a discrete component in others. This may be a documented change, or simply a production-line convenience due to a parts shortage. If you need to replace it, you should use a mica cap.<P>Re the 6287 tub: There are two different styles of tubs. The older ones can be distinguished by a terminal sticking out on the end opposite the mounting screw. Also, the terminals on the sides are separate, they don't go all the way across the body. The early versions have a single-letter suffix, while the later ones have a two- or three-letter suffix. The number which you gave, the 6287DU, is of the latter type. The parts list on the Philco Repair Bench site shows a 6287-ODU, which should be the same part. There are two different tables for this part number... you want the second table. There are only three terminals on this part, and they go all the way across the body. There is no resistor. You can determine where to connect the new capacitors by observing the existing leads when you disassemble it. They go through the rivets that hold the terminals in place.<P>HTH. Sounds like you're making good progress <IMG SRC="http://antiqueradios.com/forums/smile.gif"><P>------------------<BR>73 de Leigh W3NLB


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 Post subject: Philco radio model 620
PostPosted: Sep Tue 30, 2003 4:56 pm 
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Hi Carmine,<BR>I’m seldom wrong about PHILCO’s, every thing else I am, but not PHILCO’s.<BR>First of all, I don’t know who’s schematic you are using , but there are 2 for this 620. Number 218 and 218A and changes in models for it. As I said, I wanted to send you these, on a no charge basis in the E/Mail, but no address.<BR>If you look at number 40, it says part of 39,<BR>And 39 says twin bakelite 8035DG, and a 8035DG is a bakelite. It’s just possible that someone removed it !! .00011 as Leigh says is a mica, and the closest you can get to it is 100<BR>When reading the charts on the blocks, note that some have been changed, for instance the letter O for higher temp wax, and the letters D, G, U S, E all mean something. You can tell which lugs there wired to by looking at the chart.<BR>Number 66 is a 6287DU, is replaced by 6287 ODU and has no resistor in it . There are 3 flex resistors in it # 19 attached to the 4989 DG block, # 24 attached to the 6A7 tube and # 34 attached to the 78 tube and # 72<BR>It’s OK to use Disc capacitors, but when it says Mica, you must use Mica to get them that low.<BR>As I said before the ohms reading on the transformer is not important at this point , only that they have continuity. Finding a problem with the 2nd IF transformer is a great job!!<BR>If you will send me your E Mail address, I’ll send you the 218 and 218A schematic’s no charge. <BR>You doing great so far Carmine, any problems just post it here on the forum!! <BR><P>------------------<BR>Rick Dippolito<BR>THE PHILCO RESTORER at<BR> <A HREF="http://hometown.aol.com/philcorestorer/myhomepage/index.html" TARGET=_blank>http://hometown.aol.com/philcorestorer/myhomepage/index.html</A>


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 Post subject: Philco radio model 620
PostPosted: Oct Wed 01, 2003 6:26 am 
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Hey guys thanks for clearing some stuff up. Rick you were right. In the (Riders schematic for later production runs) it has the parts listed like you said. i have that schematic and it is not as clear as the one im using But Thanks for the offer. The one that im using is the Philco wiring diagrams parts list Vol. 1 1928 to 1936 service data.It has all these old original pamphlet with different model numbers put in a book binder. My cousin bought it at a garage sale a few years back and gave to me. It has been on my shelf with other old radio books for years and i finally got to use it with this radio. So i looked up the model 620 and it was there.On that parts list it has part 39 (.00011 MFD MICA ) part no. 30-1031. 39A (.00011 MFD MICA ) part no. 30-1031. 40 (.00011 MFD MICA ) part no. 30-1031. and when i turn the radio to the underside i do not see any thing that resembles the other three block capacitors that are in the radio.The schamatic shows 37 (2nd I.F. Transformer) part no.32-1647. it shows 39 as two 110 uuf same as (.00011) in series going to the 75 tube and 40 which is also 110uuf looks like it hooks to resistor part 73 to ground. and this is closer to what the uderside of my radio looks like the only difference is there is this large tie down that takes up 1/4 of that side of the chassis as a matter of fact it covers the 2nd I. F. Transformer pins and some of the 75 tube pins etc. But im going to check that out and see exactly what they look like but the tie down wires are so tight that its going to be difficult. but i can see under it and there is no block capacitor but i do see 3 mica capacitors on the tie down. so im going to check those out.<BR> Leigh the reason i was asking about the capacitors in parallel is because when i change the .15 paper cap in the radio i put two capacitor toghether in parallel one .1 600 volts and a .047 600 volts. i also changed the electolytic cap whose value was 16 mfd 600 volts with one 10 mfd 450 volts and in parallel with 10 mfd 160 volts if this was wrong ill change it but i dont have those values so maybe you have some suggestion.<BR> Thanks <P>------------------<BR>


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 Post subject: Philco radio model 620
PostPosted: Oct Wed 01, 2003 6:43 am 
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<BLOCKQUOTE><font>quote:</font><HR>Originally posted by carmine:<BR><B>i also changed the electolytic cap whose value was 16 mfd 600 volts with one 10 mfd 450 volts and in parallel with 10 mfd 160 volts if this was wrong ill change it but i dont have those values so maybe you have some suggestion.<BR></B><HR></blockquote><P>Carmine,<P>DO NOT turn the radio on with those electrolytics in it. They WILL blow up!!<P>When replacing capacitors, never use a part with a lower voltage rating than the original. In this case, the 600-volt cap is a little more difficult to find, but they are available. As far as the capacitance, a 22 mfd @ 600 volts would work fine, or two 10 mfd @ 600 volts in parallel.<P>One source is Allied at <A HREF="http://www.alliedelec.com/catalog/pf.asp?FN=170.pdf" TARGET=_blank>http://www.alliedelec.com/catalog/pf.asp?FN=170.pdf</A> , which is the catalog page. Lower right corner, 20 mfd 600 v tubular electrolytic, current price is $9.38 each.<P>------------------<BR>73 de Leigh W3NLB


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 Post subject: Philco radio model 620
PostPosted: Oct Wed 01, 2003 8:32 am 
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Hi<P> Why would Philco 620 need a 600 volt electrolytic? This radio uses an 80 rectifier & 42 output tube. Filter caps in the schematic I am looking at are 8 mfd. They could be replaced by 10 mfd @ 450 volts. <P> The 16 mfd @ 600 volts may have been a replacement? <P> Don't use 10 mfd @ 160 volts. As Leigh mentioned this one will blow up. <P> <P>------------------<BR>Norm


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