Philly BOL restoration problems - EH Scott Radio Enthusiasts2024-03-29T05:18:41Zhttps://ehscott.ning.com/forum/topics/philly-bol-restoration-problems?commentId=3925821%3AComment%3A93493&feed=yes&xn_auth=noregarding the failed press fi…tag:ehscott.ning.com,2021-03-06:3925821:Comment:1168892021-03-06T04:04:29.921ZDavid C. Polandhttps://ehscott.ning.com/profile/DavidCPoland
<p>regarding the failed press fit of a hex nut on a trimmer. An ARF thread offered a plausible fix. </p>
<p>Drill and tap the nut for for a small set screw. Allows adjusting the position of the nut for proper fit.</p>
<p>regarding the failed press fit of a hex nut on a trimmer. An ARF thread offered a plausible fix. </p>
<p>Drill and tap the nut for for a small set screw. Allows adjusting the position of the nut for proper fit.</p> Troy - Thanks for your readin…tag:ehscott.ning.com,2021-02-14:3925821:Comment:1021312021-02-14T01:12:32.849ZDavid C. Polandhttps://ehscott.ning.com/profile/DavidCPoland
<p>Troy - Thanks for your reading. </p>
<p>Seems to be a lot of variation with later production Philharmonics showing higher plate voltages well over 200 volts - on not only the 6J7 plate, but also the neighboring 6B8 in the scratch suppressor circuit.</p>
<p>Today I found my BOL Philly had yet another factory wiring error. The the 6B8 grid is normally at near -27 volts, on a feed from the -27 volt end of the -C divider. But when the switch is turned "on", another feed from the -6 volt tab on…</p>
<p>Troy - Thanks for your reading. </p>
<p>Seems to be a lot of variation with later production Philharmonics showing higher plate voltages well over 200 volts - on not only the 6J7 plate, but also the neighboring 6B8 in the scratch suppressor circuit.</p>
<p>Today I found my BOL Philly had yet another factory wiring error. The the 6B8 grid is normally at near -27 volts, on a feed from the -27 volt end of the -C divider. But when the switch is turned "on", another feed from the -6 volt tab on the C divider is supposed to feed to the 6B8 grid, triggering reduction of audio high frequencies at low sound levels. Instead my 6B8 grid barely dropped and the circuit did not function. A factory mistake rendered the scratch suppressor circuit inoperative.</p>
<p>This alternative -6 volt feed was wired improperly. The diagram shows this wire is supposed to connect to one end of the -C mini pot on the C divider and continue on to -6 volt lug on the -C divider. My set wire stopped at the mini pot and did not continue on to the -6 volt tap, nor any sign it was ever so wired. A temp connection from the mini pot lug to the -6 volt tap allowed the scratch suppressor to function when switched ON. Found negligible affect on other negative bias circuits when I corrected this wiring.</p>
<p></p> Hello-
I wrapped a wire aroun…tag:ehscott.ning.com,2021-02-13:3925821:Comment:1020192021-02-13T20:18:03.237ZTroy Taylorhttps://ehscott.ning.com/profile/TroyTaylor
<p>Hello-</p>
<p>I wrapped a wire around the 6J7 scratch-suppressor plate pin on my 1937 pointer-dial Philharmonic this morning and have a meter measuring the voltage right now. It is holding steady at 220VDC. A finger on the grid cap makes a very obnoxious noise in the audio.</p>
<p>From the previous postings, it seems this is behaving more like a post 1939-redesign set.</p>
<p>-Troy</p>
<p>in very snowy Edmonds, WA</p>
<p></p>
<p>Hello-</p>
<p>I wrapped a wire around the 6J7 scratch-suppressor plate pin on my 1937 pointer-dial Philharmonic this morning and have a meter measuring the voltage right now. It is holding steady at 220VDC. A finger on the grid cap makes a very obnoxious noise in the audio.</p>
<p>From the previous postings, it seems this is behaving more like a post 1939-redesign set.</p>
<p>-Troy</p>
<p>in very snowy Edmonds, WA</p>
<p></p> Robert - Great idea to wrap a…tag:ehscott.ning.com,2021-02-07:3925821:Comment:966022021-02-07T20:07:59.000ZDavid C. Polandhttps://ehscott.ning.com/profile/DavidCPoland
<p>Robert - Great idea to wrap a wire around #3 pin/plate for a measurement. Thanks.</p>
<p>Did so on my restored working pointer Philly. 6J7 plate voltage quickly settled in at 162 volts on my digital meter.</p>
<p>Advanced fidelity control and cut sensitivity control to produce a weak reception with plenty of high frequency audio and noise. Engaged the scratch suppressor and the higher frequency audio disappeared as it should. :-)</p>
<p>So,</p>
<p> 1) My…</p>
<p>Robert - Great idea to wrap a wire around #3 pin/plate for a measurement. Thanks.</p>
<p>Did so on my restored working pointer Philly. 6J7 plate voltage quickly settled in at 162 volts on my digital meter.</p>
<p>Advanced fidelity control and cut sensitivity control to produce a weak reception with plenty of high frequency audio and noise. Engaged the scratch suppressor and the higher frequency audio disappeared as it should. :-)</p>
<p>So,</p>
<p> 1) My <span style="text-decoration: underline;">pointer dial</span> Philly scratch suppressor circuit is working well, with 162 volt plate voltage, with house AC voltage about 122 volts, somewhat higher than the AC specified for testing purposes. </p>
<p> 2) I conclude the Scott voltage chart is wrong, and the 75v shown likely should read more like 150v, allowing for my reading is a bit inflated at my higher house AC voltage. In addition, provides a more typical difference compared to the 100 volt pin #4 screen voltage spec.</p>
<p> 3) I am correcting my original Riders page and my photo copies to read 150 volts for the 6J7 plate, pin 3.</p>
<p> 4) the Extensive Riders info was probably mostly developed for the 1937 pointer dial Philharmonics production. Seems likely, the 1939 redesign may have altered some resistance and voltage specification a bit for later production Beam of Light Philharmonics featuring the additional two control shafts (BOL 8 shaft) sets. But note that the Riders diagram is dated 1939 for the re-designed BOL Philharmonic.</p>
<p>*</p>
<p></p>
<p>I will stop obsessing about the 6J7 plate voltage. </p>
<p>That you are reading 225 volts and I am reading 230 suggests result of the 1939 re-design.</p>
<p>And we are both experiencing super-sensitive 6J7 grid, perhaps a result of 1939 redesign.</p>
<p>The above mentioned thread (Scratch Suppressor by Norman B.) mentions a revised B divider as well to improve voltages.</p>
<p></p> Done! I wrapped a wire aroun…tag:ehscott.ning.com,2021-02-07:3925821:Comment:960122021-02-07T05:42:07.675ZRobert Feenstrahttps://ehscott.ning.com/profile/RobertFeenstra
<p>Done! I wrapped a wire around the plate pin. Interesting, I read 225 volts with scratch on or off. Close to where you are. Looking at the 6J7 specs, the tube should be at cutoff with the grid at about -6 volts or lower. It would seem it takes quite a scratch to actually make the tube conduct. Unless, of course I totally miss understand the circuit, which is very likely!! It looks like you are in the ballpark and the schematic listed voltage is wrong.</p>
<p></p>
<p>I'm getting close…</p>
<p>Done! I wrapped a wire around the plate pin. Interesting, I read 225 volts with scratch on or off. Close to where you are. Looking at the 6J7 specs, the tube should be at cutoff with the grid at about -6 volts or lower. It would seem it takes quite a scratch to actually make the tube conduct. Unless, of course I totally miss understand the circuit, which is very likely!! It looks like you are in the ballpark and the schematic listed voltage is wrong.</p>
<p></p>
<p>I'm getting close to powering up my AM/FM Philly. While I have it on the bench, I'll do some playing with the scratch circuit to see if I can figure out what voltages are necessary to make it work. I'll generate some "scratches" and watch what it does on the scope. Should be fun!</p> Hummm.
So maybe the disturbin…tag:ehscott.ning.com,2021-02-07:3925821:Comment:960812021-02-07T04:07:12.810ZDavid C. Polandhttps://ehscott.ning.com/profile/DavidCPoland
<p>Hummm.</p>
<p>So maybe the disturbing nature of my Scratch Suppressor and the 6J7 is appropriate for a later BOL radio?</p>
<p>Robert - Be interested in your voltage of the 6J7 plate voltage with a meter prod into the tube socket from above. Save you extracting your Philly from the cabinet.</p>
<p>Hummm.</p>
<p>So maybe the disturbing nature of my Scratch Suppressor and the 6J7 is appropriate for a later BOL radio?</p>
<p>Robert - Be interested in your voltage of the 6J7 plate voltage with a meter prod into the tube socket from above. Save you extracting your Philly from the cabinet.</p> The grid on my BOL 6J7 is ver…tag:ehscott.ning.com,2021-02-06:3925821:Comment:959012021-02-06T23:40:06.285ZRobert Feenstrahttps://ehscott.ning.com/profile/RobertFeenstra
<p>The grid on my BOL 6J7 is very sensitive. A finger on it produces very loud hum/buzz. Also when I measure the voltage.</p>
<p></p>
<p>If I get a chance, I'll pull my chassis and measure the plate voltage. It's kind of pain to get in and out and have it operating when out!</p>
<p></p>
<p>To be honest, I'm not even sure my scratch suppressor even works the way it is supposed to! </p>
<p>The grid on my BOL 6J7 is very sensitive. A finger on it produces very loud hum/buzz. Also when I measure the voltage.</p>
<p></p>
<p>If I get a chance, I'll pull my chassis and measure the plate voltage. It's kind of pain to get in and out and have it operating when out!</p>
<p></p>
<p>To be honest, I'm not even sure my scratch suppressor even works the way it is supposed to! </p> Scott - Had not considered t…tag:ehscott.ning.com,2021-02-06:3925821:Comment:958672021-02-06T21:20:02.962ZDavid C. Polandhttps://ehscott.ning.com/profile/DavidCPoland
<p>Scott - Had not considered the 75 volt plate voltage spec for the 6J7 might be a typo. </p>
<p>*</p>
<p>One difference between my Pointer and BOL receivers. Touching with my finger the 6J7 grid cap is not a loud audio event for the pointer Philly. But my subject BOL, touching the 6J7 grid is a huge noise event.</p>
<p>I know there were a series of changes made mid 1939 to the Philly receiver circuits. I believe my 8 control BOL is later by virtue of the 1940 Strad red band dial with upper…</p>
<p>Scott - Had not considered the 75 volt plate voltage spec for the 6J7 might be a typo. </p>
<p>*</p>
<p>One difference between my Pointer and BOL receivers. Touching with my finger the 6J7 grid cap is not a loud audio event for the pointer Philly. But my subject BOL, touching the 6J7 grid is a huge noise event.</p>
<p>I know there were a series of changes made mid 1939 to the Philly receiver circuits. I believe my 8 control BOL is later by virtue of the 1940 Strad red band dial with upper logging scale. However, my chassis was punched for the early scratch suppressor switch below the tuning knob. Kent says my set # RR-112 suggests a much earlier build and speculates mine could have been returned for factory updating, perhaps even to add remote control, the dial and other updates. The volume control had been replaced before I acquired this BOL set, with a 500K control with appropriate 50K tap. My set has a vitreous ceramic B+ voltage divider, a suspected replacement of a candohm.</p>
<p>There were some lengthy Philly restoration threads on the Scott site late 2014 and early 2015. One entitled Philharmonic Record Scratch 3/24/2015 discusses this circuit and issues involving the 6B8 tube. Norman's problem was overacting of the circuit when engaged. I do not note a change engaging the circuit by listening. I have now installed an older 6B8-G hot branded Sylvania - no difference noted. Next I will try a temp shunting a 560K resistor from 6B8 screen to ground as mentioned in this thread.</p>
<p>*</p>
<p>Audio hum still a problem. Used the screw driver tip to ground on a number of riveted ground lugs and tightened those held by nuts to no avail. </p>
<p> </p>
<p></p> I use an RCA VTVM I built fro…tag:ehscott.ning.com,2021-02-06:3925821:Comment:958002021-02-06T19:51:46.281ZDavid C. Polandhttps://ehscott.ning.com/profile/DavidCPoland
<p>I use an RCA VTVM I built from a kit in high school about 1960.</p>
<p>I also checked that plate voltage socket pin # 3 is active with voltage prod into the socket from above.</p>
<p>The 6J7-G negative grid voltages varies from -20v (off) to -16v (on). Running off the two taps of the -C divider.</p>
<p>There is no 6J7 plate voltage change switching scratch suppressor between on and off.</p>
<p>Touching (and releasing) the 6J7 grid cap with VTVM's DC volt prod produces a tremendous audio pop,…</p>
<p>I use an RCA VTVM I built from a kit in high school about 1960.</p>
<p>I also checked that plate voltage socket pin # 3 is active with voltage prod into the socket from above.</p>
<p>The 6J7-G negative grid voltages varies from -20v (off) to -16v (on). Running off the two taps of the -C divider.</p>
<p>There is no 6J7 plate voltage change switching scratch suppressor between on and off.</p>
<p>Touching (and releasing) the 6J7 grid cap with VTVM's DC volt prod produces a tremendous audio pop, as does touching it to the pin 3 of the socket.</p> I don't think that 75v is cor…tag:ehscott.ning.com,2021-02-06:3925821:Comment:957162021-02-06T19:19:37.826ZScott Seickelhttps://ehscott.ning.com/profile/ScottSeickel
<p>I don't think that 75v is correct. Your 230v sounds more like it. I don't have time to pull a chassis right now to verify it. </p>
<p></p>
<p><a href="https://storage.ning.com/topology/rest/1.0/file/get/8526891094?profile=original" target="_blank" rel="noopener"><img src="https://storage.ning.com/topology/rest/1.0/file/get/8526891094?profile=RESIZE_710x" class="align-full"/></a></p>
<p>I don't think that 75v is correct. Your 230v sounds more like it. I don't have time to pull a chassis right now to verify it. </p>
<p></p>
<p><a href="https://storage.ning.com/topology/rest/1.0/file/get/8526891094?profile=original" target="_blank" rel="noopener"><img src="https://storage.ning.com/topology/rest/1.0/file/get/8526891094?profile=RESIZE_710x" class="align-full"/></a></p>