[AMRadio] Heath HO 10 Monitor Scope
Have replaced bad 3RP1 cathode tube in my HO 10 and tested all other tubes. Have changed the two [EMAIL PROTECTED] capacitors. It is working however not up to PAR. All controls work. The current problem is that when in the trapezoid pattern monitoring AM transmitted signal, the horizontal width of the trapezoid doesn't completely fill out to a symetrical point. The horizontal position and horizontal gain pots work except that there doesn't seem to be enough horizontal gain to cause the trapezoid to fully display the full signal. I have a properly working SB 610 that shows clearly my transmitted AM signal. The HO 10 doesn't fill out the trapezoid symetrically to a point. I suspect a resistor in the horizontal gain circuit having changed value or maybe a suspect capacitor. Are there any commonly known culprits that cause this loss of horizontal gain? Naturally, I am lazy by nature, and would rather pick your brains than use my feeble brain. What are your thoughts based on your vast knowledge and EXPERIENCE??? Thanks and 73, John, K5PGW Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Heath HO 10 Monitor Scope
For starters, check the resistors in the cathode and plate circuit of the 6C10 Horizontal amp. section. Try a new 6C10. Check the input (2 mfd) and output (.22 mfd) caps for leakage. You might also check the 6BN8 RF Demodulator section and components. Pete, wa2cwa http://www.manualman.com On Sun, 24 Feb 2008 10:11:07 -0800 (PST) John King [EMAIL PROTECTED] writes: Have replaced bad 3RP1 cathode tube in my HO 10 and tested all other tubes. Have changed the two [EMAIL PROTECTED] capacitors. It is working however not up to PAR. All controls work. The current problem is that when in the trapezoid pattern monitoring AM transmitted signal, the horizontal width of the trapezoid doesn't completely fill out to a symetrical point. The horizontal position and horizontal gain pots work except that there doesn't seem to be enough horizontal gain to cause the trapezoid to fully display the full signal. I have a properly working SB 610 that shows clearly my transmitted AM signal. The HO 10 doesn't fill out the trapezoid symetrically to a point. I suspect a resistor in the horizontal gain circuit having changed value or maybe a suspect capacitor. Are there any commonly known culprits that cause this loss of horizontal gain? Naturally, I am lazy by nature, and would rather pick your brains than use my feeble brain. What are your thoughts based on your vast knowledge and EXPERIENCE??? Thanks and 73, John, K5PGW __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Heath HO 10 Monitor Scope
John, perhaps this copied email I saved will help you and others repairing the Heathkit scopes. Perhaps some of this can helpApplies to SB-6510 and HO-10 73, Larry KC8JX Owner of a SB-610 and two HO-10's *** March 14, 2007: By carl lowry [EMAIL PROTECTED] I redo the SB-610s everyday. Infact there are 8 of them in my workshop right now to be restored. The 610s were manufactured by Heathkit between 1968 and 1972. They are older than some of our recent Hams.. but many of us broke our teeth on Heathkit. Every 610 I get in here I replace all the resistors and all the caps. It takes me about 15 hours to undo replace all the components. When the Control Pots are stiff or frozen you've got to disassemble them clean them up relub. The Selenium Rectifiers I replace with 1N4007 Diodes. I have really not found any resistors or caps in the units to spec at what they originally were when first manufactured. After all they are 35 years vintage. We all change after those many years. The lack of trace wave width (TWW) can be contributed to the .05mfd cap going to pin 3 on Horizonal Gain Pot which is a 1 megohm. Also look at the Horizonal Position Pot circuit which has a .1mfd cap on pin 3. Like one of the other guys mentioned Look at the Intensity circuit. Also look at the Focus Pot next to it. I would replace the 2 Caps and the 3 resistors ( 330k 3.3m ). If you need the Mouser Part Numbers please e-mail me I will be glad to Fax you all the Mouser part numbers. Good luck. Carl. ** --- John King [EMAIL PROTECTED] wrote: Have replaced bad 3RP1 cathode tube in my HO 10 and tested all other tubes. Have changed the two [EMAIL PROTECTED] capacitors. It is working however not up to PAR. All controls work. The current problem is that when in the trapezoid pattern monitoring AM transmitted signal, the horizontal width of the trapezoid doesn't completely fill out to a symetrical point. The horizontal position and horizontal gain pots work except that there doesn't seem to be enough horizontal gain to cause the trapezoid to fully display the full signal. I have a properly working SB 610 that shows clearly my transmitted AM signal. The HO 10 doesn't fill out the trapezoid symetrically to a point. I suspect a resistor in the horizontal gain circuit having changed value or maybe a suspect capacitor. Are there any commonly known culprits that cause this loss of horizontal gain? Naturally, I am lazy by nature, and would rather pick your brains than use my feeble brain. What are your thoughts based on your vast knowledge and EXPERIENCE??? Thanks and 73, John, K5PGW Looking for last minute shopping deals? Find them fast with Yahoo! Search. http://tools.search.yahoo.com/newsearch/category.php?category=shopping __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] TH vs TL
Not sure if one type requires much more power to drive, or the drive circuit is wrong. The TL versions, like the 812(a) needs lots more VOLTAGE to drive the grid. It might just be a matter of the grid input circuit developing the voltage In the arrl handbook, they have the 100 TH taking 18 watts of drive, the TL 20. Not a big difference Also, anyone ever notice the arrl handbooks had a typo on the TH-TL listings for class B service, the 100TH does 3000 volts, 215ma for 650 watts out, the 100TL has the same 3000 volts and 215 ma for 450 watts out. They never corrected it as far as I know Brett N2DTS - Original Message - From: D. Chester [EMAIL PROTECTED] To: amradio@mailman.qth.net Sent: Saturday, February 23, 2008 9:24 PM Subject: Re: [AMRadio] TH vs TL The Eimac designation TH and TL mean Triode High mu and Triode Low mu. Generally, the high mu versions of transmitting triodes work better as class-B modulators (or rf linears), while the TL's work better in class-C. But either version have specifications listed for either service. But I would recommend the adjusting the circuit for correct grid bias and grid drive current for each type of tube, not just swapping out the tubes with no changes in parameters. The low mu's run lower grid current and higher bias, while the corresponding high mu's run higher grid current with lower bias voltage. See the manufacturers' data sheets, or if not available, see the tube charts in the ARRL or West Coast Handbooks. There are other similar sibling sets of RCA tubes; the 810 is the higher mu version; the 8000 the low mu. 203A higher mu, 211 low mu. 811(A) high mu, 812(A) lower mu. I have used both 810's and 8000's in the rf final of my transmitter. The lower mu 8000's require about 75% as much driving power for class C plate modulated service as the 810's. The HF-300's that I am now have class-C operating parameters very similar to 8000's. All I had to change was the mechanical plate connections; the grid bias, grid current and grid leak resistor work equally well with each tube, and re-neutralise. With 810's I had to use a lower value of grid leak resistor plus re-neutralise. Don k4kyv __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] TL and TH tubes
k4kyv provided good general rules for when the hi and lo mu triodes were suited for transmitters. Low mu triodes, as class C devices, would be driven hard into grid current. Another big use of these devices was and still is in dielectric and induction heating systems. These applications often run the amplifier (or usually just a power oscillator) with widely varying loads, creating large mismatches. Instead of having 50 ohm circuits, these things are direct coupled to the load, such as having ferrous metals heated in a tank inductor, or having lossy plastics in an air tank capacitor. As such, when the load shifts from zero to full load, grid current changes greatly. A high mu triode oscillator could change grid current as much as to stop oscillation, or to seriously overdrive the grid on the tube, depending on the load. By using a low mu tube, this fluctuation is much less severe, and the grid current can remain in the 'safe' region for the tube as well as keeping the oscilla tor going. Thats why tubes like 8000 were seen in diathermy machine. In very large systems (50 kW), would use 3CW30,000H1 or H3 whereas such a low mu tube would be les desirable for transmitters, as they would need a bigger driver stage plus larger grid bias voltages (for cutoff conditions). 73 John K5PRO Message: 2 Date: Sat, 23 Feb 2008 20:24:37 -0600 From: D. Chester [EMAIL PROTECTED] Subject: Re: [AMRadio] TH vs TL To: amradio@mailman.qth.net The Eimac designation TH and TL mean Triode High mu and Triode Low mu. Generally, the high mu versions of transmitting triodes work better as class-B modulators (or rf linears), while the TL's work better in class-C. But either version have specifications listed for either service. But I would recommend the adjusting the circuit for correct grid bias and grid drive current for each type of tube, not just swapping out the tubes with no changes in parameters. The low mu's run lower grid current and higher bias, while the corresponding high mu's run higher grid current with lower bias voltage. See the manufacturers' data sheets, or if not available, see the tube charts in the ARRL or West Coast Handbooks. There are other similar sibling sets of RCA tubes; the 810 is the higher mu version; the 8000 the low mu. 203A higher mu, 211 low mu. 811(A) high mu, 812(A) lower mu. I have used both 810's and 8000's in the rf final of my transmitter. The lower mu 8000's require about 75% as much driving power for class C plate modulated service as the 810's. The HF-300's that I am now have class-C operating parameters very similar to 8000's. All I had to change was the mechanical plate connections; the grid bias, grid current and grid leak resistor work equally well with each tube, and re-neutralise. With 810's I had to use a lower value of grid leak resistor plus re-neutralise. Don k4kyv __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] TH/TL More
I'd like to thank all that responded to my question regarding the TH and TL designators. I did know the high mu and low mu difference, but I had always thought (due, I suspect, to seeing TH tubes as RF amplifiers in so many magazine and handbook articles) that the TH was the RF amp, and that the TL was the audio amp. Now, I'm faced with another challenge. I am planning to rebuild a transmitter I first built in the early 1990s. It used a push-pull pair of 6C21s, modulated by a pair of 304TLs. It worked great, and, according to on-the-air reports, sounded good. But, it was really big and heavy, overly complicated, and, due to my wanting it to look like an old fashion rig, caused RFI/TVI for blocks. I grew tired of neighbors marching down the street, bearing torches and chanting evil things. So, I tore it apart. Now, I want to rebuild it. I have spent several hours the last couple of days hipoting 450TLs, 450THs and 304TLs. One of my 6C21s has lost it's vacuum, so I'll be using 450TLs in the (well-shielded) final. Now I'm thinking that I may use 450THs as the modulators, instead of 304TLs. The hobby is supposed to be fun, and I think that would be fun. Four tall tubes. Well, there we go, getting big again. Anyone see anything wrong with that? I ran the 304TLs in AB1 the last time I built the rig. I'd like to run AB1 this time, as well, unless something has changed in the last 15 years. I don't see any specs for the 450TH in AB1, just AB2. Anyone have any numbers for that tube in AB1 they'd care to share? I don't find any amateur web-sites with much how to do it information on building modulators for AB1. The handbooks (that I have) all feature class B. Are there any sites I could visit with such information? 73, Barrie, W7ALW, DN36au, QRV 6M, 432 1296 EME __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
