Military projector amp - last edited 9/26/22 - layout help needed
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Re: Military projector amp problem (Bell and Howell 614/AQ2A) - speaker distorting/overworked
Thank you both for the thoughtful response about voltage and exact parts to mod, I appreciate it! Time to put together my next order list.
The place where I typically order parts (Amplified Parts) from doesn't carry 1000uf or 2200uf caps - where do you find them? Mouser, or ??? I need to expand my parts ordering options.
The place where I typically order parts (Amplified Parts) from doesn't carry 1000uf or 2200uf caps - where do you find them? Mouser, or ??? I need to expand my parts ordering options.
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Re: Military projector amp problem (Bell and Howell 614/AQ2A) - speaker distorting/overworked
Mouser should have them.
Also, FYI, Randall Aiken has some great technical information on his web site:
https://www.aikenamps.com/index.php/des ... amplifiers covers most of what we've been discussing in this thread.
Also, FYI, Randall Aiken has some great technical information on his web site:
https://www.aikenamps.com/index.php/des ... amplifiers covers most of what we've been discussing in this thread.
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Re: Military projector amp problem (Bell and Howell 614/AQ2A) - speaker distorting/overworked
ZP's right about the very low voltage cathode bypass cap values on the preamp tubes. Those voltages circle around a few volts.
I wrote 25V because of the physical size of those lower value caps. In aestetics it's all about balance
I wrote 25V because of the physical size of those lower value caps. In aestetics it's all about balance
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Re: Military projector amp problem (Bell and Howell 614/AQ2A) - speaker distorting/overworked
A few volts? I would say around just one volt. I get what you mean about the aesthetics, but I wonder if higher voltage-rated electrolytics might not have poorer high frequency performance
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Re: Military projector amp problem (Bell and Howell 614/AQ2A) - speaker distorting/overworked
Looks like the 100uf cap, that is suggested to change to 1000 or 2200, is labeled as a 25v cap. I'll keep the other caps within a lower range with frequency response in mind.
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Re: Military projector amp problem (Bell and Howell 614/AQ2A) - speaker distorting/overworked
That's correct, the power tube cathode cap is higher voltage, but still not super high. If it had 25V, you can go between 25 to 50V depending on what's available with little concern for size. The 2200uF caps I use in my EL84 powered amps are rate 40V, and the average voltage there is about 12VDC.
Thanks,
Josh
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Re: Military projector amp problem (Bell and Howell 614/AQ2A) - speaker distorting/overworked
@yello,
As I was studying the Bell & Howell amplifier schematic, it occurred to me that you have most of the parts there for a 10W version of a F***er Tweed Deluxe, either the 5D3 or 5E3 variant. So for a little extra challenge and some awesome sounds, I recommend converting one of your B&H amps to a Tweed Deluxe. I tend to think of the 5E3 as Leo's fire-breathing equivalent of Marshall's 18W - https://ampwares.com/schematics/deluxe_5e3.pdf
While the 5E3 is the most popular of the two, personally, I think the 5D3, with its paraphase PI, has the sweeter tone http://www.thetubestore.com/lib/thetube ... ematic.pdf
For support, our companion site ppwatt.com has a 5E3 mods forum - http://www.ppwatt.com/5e3-mods
Also lots of good information on https://robrobinette.com/5e3_Modifications.htm
As I was studying the Bell & Howell amplifier schematic, it occurred to me that you have most of the parts there for a 10W version of a F***er Tweed Deluxe, either the 5D3 or 5E3 variant. So for a little extra challenge and some awesome sounds, I recommend converting one of your B&H amps to a Tweed Deluxe. I tend to think of the 5E3 as Leo's fire-breathing equivalent of Marshall's 18W - https://ampwares.com/schematics/deluxe_5e3.pdf
While the 5E3 is the most popular of the two, personally, I think the 5D3, with its paraphase PI, has the sweeter tone http://www.thetubestore.com/lib/thetube ... ematic.pdf
For support, our companion site ppwatt.com has a 5E3 mods forum - http://www.ppwatt.com/5e3-mods
Also lots of good information on https://robrobinette.com/5e3_Modifications.htm
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Re: Military projector amp problem (Bell and Howell 614/AQ2A) - speaker distorting/overworked
I thought the 6G3 was the fire-breathing monster Leo created!?zaphod_phil wrote: βSat 02/12/22 1:44 pm@yello,
As I was studying the Bell & Howell amplifier schematic, it occurred to me that you have most of the parts there for a 10W version of a F***er Tweed Deluxe, either the 5D3 or 5E3 variant. So for a little extra challenge and some awesome sounds, I recommend converting one of your B&H amps to a Tweed Deluxe. I tend to think of the 5E3 as Leo's fire-breathing equivalent of Marshall's 18W - https://ampwares.com/schematics/deluxe_5e3.pdf
While the 5E3 is the most popular of the two, personally, I think the 5D3, with its paraphase PI, has the sweeter tone http://www.thetubestore.com/lib/thetube ... ematic.pdf
For support, our companion site ppwatt.com has a 5E3 mods forum - http://www.ppwatt.com/5e3-mods
Also lots of good information on https://robrobinette.com/5e3_Modifications.htm
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Re: Military projector amp problem (Bell and Howell 614/AQ2A) - speaker distorting/overworked
No, the 6G3 Brown Deluxe is a very tamed-down version, thanks to its negative feedback. It's a much later product than the 5D3/5E3 Tweed Deluxes and Leo's amp designs got cleaner and cleaner in each successive generation.
Further discussion on this topic will probably best be continued on our companion site, www.ppwatt.com
Further discussion on this topic will probably best be continued on our companion site, www.ppwatt.com
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Re: Military projector amp problem (Bell and Howell 614/AQ2A) - speaker distorting/overworked
Just keep in mind that in cathode-biased amplifiers, the cathode voltage will swing upward on signal envelope peaks. So I tend to use higher voltage rated caps on the power tube cathodes.JMPGuitars wrote: βSat 02/12/22 12:25 pmThat's correct, the power tube cathode cap is higher voltage, but still not super high. If it had 25V, you can go between 25 to 50V depending on what's available with little concern for size. The 2200uF caps I use in my EL84 powered amps are rated 40V, and the average voltage there is about 12VDC.
Thanks,
Josh
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Re: Military projector amp problem (Bell and Howell 614/AQ2A) - speaker distorting/overworked
I use the 63V big barrels mostlyzaphod_phil wrote: βMon 02/14/22 2:29 pmJust keep in mind that in cathode-biased amplifiers, the cathode voltage will swing upward on signal envelope peaks. So I tend to use higher voltage rated caps on the power tube cathodes.JMPGuitars wrote: βSat 02/12/22 12:25 pmThat's correct, the power tube cathode cap is higher voltage, but still not super high. If it had 25V, you can go between 25 to 50V depending on what's available with little concern for size. The 2200uF caps I use in my EL84 powered amps are rated 40V, and the average voltage there is about 12VDC.
Thanks,
Josh
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Re: Military projector amp problem (Bell and Howell 614/AQ2A) - speaker distorting/overworked
https://youtube.com/shorts/n6e3QpzRGJA?feature=share
Same amp type, different amp, different problem.
There is a static on the notes. It is different than the overworked clubby speaker issue of the other one. Any idea what might typically cause this?
I have eliminated the speaker, tubes, guitar, or cable as the cause, itβs somewhere in the circuit.
I have replaced the power filter caps, but not yet the 100v 25uf Mallory cap. I also replaced a coupling cap that was very microphonic. The static issue did not change before or after that cap.
Any ideas?
Same amp type, different amp, different problem.
There is a static on the notes. It is different than the overworked clubby speaker issue of the other one. Any idea what might typically cause this?
I have eliminated the speaker, tubes, guitar, or cable as the cause, itβs somewhere in the circuit.
I have replaced the power filter caps, but not yet the 100v 25uf Mallory cap. I also replaced a coupling cap that was very microphonic. The static issue did not change before or after that cap.
Any ideas?
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Re: Military projector amp problem (Bell and Howell 614/AQ2A) - speaker distorting/overworked
If that is signal related you'll be better off with a scope . Starting at the input.yello wrote: βMon 02/21/22 11:09 pmhttps://youtube.com/shorts/n6e3QpzRGJA?feature=share
Same amp type, different amp, different problem.
There is a static on the notes. It is different than the overworked clubby speaker issue of the other one. Any idea what might typically cause this?
I have eliminated the speaker, tubes, guitar, or cable as the cause, itβs somewhere in the circuit.
I have replaced the power filter caps, but not yet the 100v 25uf Mallory cap. I also replaced a coupling cap that was very microphonic. The static issue did not change before or after that cap.
Any ideas?
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Re: Military projector amp problem (Bell and Howell 614/AQ2A) - speaker distorting/overworked
Unfortunately I don't have a scope.
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Re: Military projector amp problem (Bell and Howell 614/AQ2A) - speaker distorting/overworked
That makes it harder. The only option is to start replacing parts one by one.. or buya scope. A Siglent isn't expensive
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Re: Military projector amp problem (Bell and Howell 614/AQ2A) - speaker distorting/overworked
Is there a certain model Siglent you recommend?
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Re: Military projector amp problem (Bell and Howell 614/AQ2A) - speaker distorting/overworked
I have the 1102 CML
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Re: Military projector amp problem (Bell and Howell 614/AQ2A) - speaker distorting/overworked
That depends on your budget. Bieworm has the SDS1102CML+ which is $299. The SDS1104X-E is $499, and a great scope. I use the SDS2104X+ (upgraded to SDS2504X+).
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Re: Military projector amp problem (Bell and Howell 614/AQ2A) - speaker distorting/overworked
While I consider the scope purchase, and potentially wait for it to arrive, are there particular components to consider replacing first like disc capacitors (I already replaced one that was microphonic), or particular parts of the circuit to start exploring in?
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Re: Military projector amp problem (Bell and Howell 614/AQ2A) - speaker distorting/overworked
Don't start replacing stuff randomly. You might create other problems along the way.
Try the non destructive way first
You could try eliminating what's good or bad when you take another same amp.
Take the power tubes out of this one.. make a long alligator clip wire and clip it between the same points in both amps. Always the grid input of a preamp triode.. starting from V1
This is what I did at some point when I couldn't find the problem in an amp. Watch out.. it's noisy too with the long antenna wire
But you should get the scope! You're not planning on stopping the amp prodding business anytime soon me guesses
Still recommended as plan A, the scoping. That will definitely give you more insights you will benefit from in the future
Try the non destructive way first
You could try eliminating what's good or bad when you take another same amp.
Take the power tubes out of this one.. make a long alligator clip wire and clip it between the same points in both amps. Always the grid input of a preamp triode.. starting from V1
This is what I did at some point when I couldn't find the problem in an amp. Watch out.. it's noisy too with the long antenna wire
But you should get the scope! You're not planning on stopping the amp prodding business anytime soon me guesses
Still recommended as plan A, the scoping. That will definitely give you more insights you will benefit from in the future
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