I have a Packard Bell 7TU12 set-up I pulled from an old console. The set-up also has a DPA30-4 tuner/control. I'd like to use just the amp, but I'm not sure how to wire it. I think I can trace the on/off switch if I power it up and run it, but I'd like to find out if anyone can steer me in the right direction. I'll also need to put some inputs on it, and I'm not completely sure how to go about finding them. The power switch and input connectors are on the tuner/control section which is hooked up via a 12 pin connector.
I've searched the web and have come up with nothing yet.
The amp has two EL84 tubes/channel and one 9-pin tube/channel that I can't identify. It has 4008 printed on it and E2, K8, and CO printed on it as well. All the tubes are Raytheon/Packard Bell. Judging by drawings that seem similar to this amp, pin 2 on the 9-pin tube is the input. I don't know that all 9-pin tubes in this configuration are the same though.
I can handle recapping it, but I'm not sure about connecting a power switch (amperage too?), a volume control, or input connectors. If I can figure out the "input tube" I can figure out the input connector and a volume control.
Any help will be greatly appreciated. I need a coach on this one.
Thanks,
Mike
I've searched the web and have come up with nothing yet.
The amp has two EL84 tubes/channel and one 9-pin tube/channel that I can't identify. It has 4008 printed on it and E2, K8, and CO printed on it as well. All the tubes are Raytheon/Packard Bell. Judging by drawings that seem similar to this amp, pin 2 on the 9-pin tube is the input. I don't know that all 9-pin tubes in this configuration are the same though.
I can handle recapping it, but I'm not sure about connecting a power switch (amperage too?), a volume control, or input connectors. If I can figure out the "input tube" I can figure out the input connector and a volume control.
Any help will be greatly appreciated. I need a coach on this one.
Thanks,
Mike
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Mike,
As is to be expected, I'm biased and STRONGLY suggest a triode wired "El Cheapo" variant be fitted into that old chassis.
Dave's point about the power trafo's heft is spot on. It's highly likely that the tuner/control chassis got its power from the amp's chassis. OTOH, those O/P trafos seem a tad flimsy. The reduced power O/P of triode mode "finals" makes magnetic headroom available for the low freq. error correction signal loop NFB generates. Reduced power O/P is traded for improved fidelity, particularly at the bottom of the audio band.
Any number of speaker designs will perform well mated to 6 honest WPC.
Can a photo of the underside be provided?
As is to be expected, I'm biased and STRONGLY suggest a triode wired "El Cheapo" variant be fitted into that old chassis.
Dave's point about the power trafo's heft is spot on. It's highly likely that the tuner/control chassis got its power from the amp's chassis. OTOH, those O/P trafos seem a tad flimsy. The reduced power O/P of triode mode "finals" makes magnetic headroom available for the low freq. error correction signal loop NFB generates. Reduced power O/P is traded for improved fidelity, particularly at the bottom of the audio band.
Any number of speaker designs will perform well mated to 6 honest WPC.
Can a photo of the underside be provided?
Thanks Eli,
I'm going to replace the 4 coupling caps with Audiocap PPT Theta 0.22uF 600V Film/Foil Capacitors
http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=027-714&scqty=4
and the one larger orange cap with Jantzen 100uF 400V Crosscap Capacitor
http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=027-956&scqty=1
Do those caps look like the right ones to use?
Also, for a main circuit breaker, what amperage should I use?
I'm not familiar with the El Cheapo. Can you give me some info on it: cost, additional parts, etc?
Thanks for your help.
Mike
I'm going to replace the 4 coupling caps with Audiocap PPT Theta 0.22uF 600V Film/Foil Capacitors
http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=027-714&scqty=4
and the one larger orange cap with Jantzen 100uF 400V Crosscap Capacitor
http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=027-956&scqty=1
Do those caps look like the right ones to use?
Also, for a main circuit breaker, what amperage should I use?
I'm not familiar with the El Cheapo. Can you give me some info on it: cost, additional parts, etc?
Thanks for your help.
Mike
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Mike,
Replacing the coupling caps. is a good idea, as they could be leaky. Replacing ALL electrolytic caps. is mandatory. Pay close attention to the multi-section can part, which is in the PSU. 'Lytics literally dry out over time. Either Panasonic ECQ-P(U) or 716P series Orange Drops are quite suitable in the coupling positions and they are modestly priced. A high quality industrial grade 'lytic, from either Panasonic or Nichicon, is satisfactory for the 100 μF./400 WVDC part.
Jim McShane should have the stuff you need, at a fair price.
You have mail!
The LENGTHY saga of "El Cheapo" can be found here.
What tube type is the rectifier? I suspect a 5U4 is installed.
Replacing the coupling caps. is a good idea, as they could be leaky. Replacing ALL electrolytic caps. is mandatory. Pay close attention to the multi-section can part, which is in the PSU. 'Lytics literally dry out over time. Either Panasonic ECQ-P(U) or 716P series Orange Drops are quite suitable in the coupling positions and they are modestly priced. A high quality industrial grade 'lytic, from either Panasonic or Nichicon, is satisfactory for the 100 μF./400 WVDC part.
Jim McShane should have the stuff you need, at a fair price.
You have mail!
The LENGTHY saga of "El Cheapo" can be found here.What tube type is the rectifier? I suspect a 5U4 is installed.
Eli Duttman said:
Mike,
I note that you have Fonkens. We have an El Cheapo variant (EL84 Class A triode, no global feedback, all Solen PS caps, using an HH Scott LK48 as donor). This 3.2 W wonder happily drives Fonkens -- matter of fact that amp, with our experimental set of FE127eN champhered on all 4 front edges was declared best match yet for a friend's new condo. He has been struggling to get something he could live with with Carina and FE126eN Hornshoppe Horns or Cain & Cain Abbys. We loaned him the El Cheapo, Fonkens, and a set of Fonken167 to see if it could help him with his logjam.
You wouldn't suffer a hardship turning your donor into one of these.
dave
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Dave,
Given 97+ dB. efficient speakers, I can see using a Class "A" operating point for the "finals". No NFB is (IMO) out of the question with the Packard/Bell O/P "iron". Look at the difference in quality between PB and Scott. Tolerable bass extension will not happen without help from NFB. AAMOF, I would not use anything bigger than 68 nF. in the high pass filter.
Given 97+ dB. efficient speakers, I can see using a Class "A" operating point for the "finals". No NFB is (IMO) out of the question with the Packard/Bell O/P "iron". Look at the difference in quality between PB and Scott. Tolerable bass extension will not happen without help from NFB. AAMOF, I would not use anything bigger than 68 nF. in the high pass filter.
Thanks Dave,
Eli has emailed the schematic for the el cheapo. I'm new to working with tubes, so that's why I'm working with the model I salvaged. I'm not sure what all I would need to do to bring what I have up to the el cheapo. The nice thing about it is that it looks like I can get the amp I have going, and then get the parts I need to make it into an el cheapo, glean all I can from all of you that know this area, and do the mods then.
I looked at the Solon caps through Madisound. My sectional PS cap has two sections of "40MFD 450V" and two sections of "20MFD 450V". All I could find on the Madisound site was 40uf and 20uf, but they were both rated at 400 volts. Am I safe to assume that an old cap labeled with "MFD" is actually the same as microfards? Also, how critical is 450 volts compared to 400 volts in this application. If those would work, could I leave the old PS cap standing as is, for looks, and put the new caps on the underside, bypassing/eliminating the old can-cap.
One other mod I'd like to do is to beef up the OT's too.
As for the Fonkens, I really like them. I've played them about 50 hours, so from what I've read, they need at least another 50 to break in. They aren't enabled, but I did get some puzzle-coat and I'm looking for some Dammer. I'm also looking for some wool felt, but I've not found any yet (any suggestions?). So far, the mids sound kind of shouty. I used the equalizer on foobar, and that tamed them pretty well. I'm hoping a full break in will tame them some more, and then maybe the Dammer and Puzzle-coat will fine tune them even further. I'll attach a phot of my Fonkens. Not much too look at yet. Once I get them lined or stuffed to where I like the sound, I'l veneer them and finish them.
Thanks for all you do for the DIY world and thanks for your input on my project.
Eli has emailed the schematic for the el cheapo. I'm new to working with tubes, so that's why I'm working with the model I salvaged. I'm not sure what all I would need to do to bring what I have up to the el cheapo. The nice thing about it is that it looks like I can get the amp I have going, and then get the parts I need to make it into an el cheapo, glean all I can from all of you that know this area, and do the mods then.
I looked at the Solon caps through Madisound. My sectional PS cap has two sections of "40MFD 450V" and two sections of "20MFD 450V". All I could find on the Madisound site was 40uf and 20uf, but they were both rated at 400 volts. Am I safe to assume that an old cap labeled with "MFD" is actually the same as microfards? Also, how critical is 450 volts compared to 400 volts in this application. If those would work, could I leave the old PS cap standing as is, for looks, and put the new caps on the underside, bypassing/eliminating the old can-cap.
One other mod I'd like to do is to beef up the OT's too.
As for the Fonkens, I really like them. I've played them about 50 hours, so from what I've read, they need at least another 50 to break in. They aren't enabled, but I did get some puzzle-coat and I'm looking for some Dammer. I'm also looking for some wool felt, but I've not found any yet (any suggestions?). So far, the mids sound kind of shouty. I used the equalizer on foobar, and that tamed them pretty well. I'm hoping a full break in will tame them some more, and then maybe the Dammer and Puzzle-coat will fine tune them even further. I'll attach a phot of my Fonkens. Not much too look at yet. Once I get them lined or stuffed to where I like the sound, I'l veneer them and finish them.
Thanks for all you do for the DIY world and thanks for your input on my project.
Attachments
mikje said:
I think we used all 32 uF 630V caps. They also have these as cans you can mount above the chassis, they are space hogs. A choke is a good idea too. We use 1 10H, 100mA Hammond for each channel.
The picture of your Fonken is small, but something didn't look quite right to me, so i comped it against one of our builds. Looks like your ports are a bit big. What are the actual measured dimensions?
The box definitely needs that damping, otherwise it is an echo chamber. Break-in goes a long way to reduce shout, and the damar trifoil + puzzlekoat kills the contribution of the 7k peak and reduces cone self-noise dramatically. Mail me if you are unsure of any part of that treatment.
dave
Dave,
The ports are 3 and an eighth inches by three eighths of an inch. Uh oh?
I have some "pillow stuffing" in the cabinets for now, but would like to find some wool felt. I also plan on ordering some acoustic damping foam from Parts Express when I order the parts for my amp. Any opinions on the acoustic damping foam?
So, are you saying that 32UF 630V caps would probably work on my amp? Can you explain where the chokes would go?
Mike
The ports are 3 and an eighth inches by three eighths of an inch. Uh oh?
I have some "pillow stuffing" in the cabinets for now, but would like to find some wool felt. I also plan on ordering some acoustic damping foam from Parts Express when I order the parts for my amp. Any opinions on the acoustic damping foam?
So, are you saying that 32UF 630V caps would probably work on my amp? Can you explain where the chokes would go?
Mike
mikje said:
From the CAD document "Ports are ~ 75mm (2 15/16") long by 9.5mm (3/8") thick - 3 per side".
That makes your ports a total of 3x 3/16" = 9/16" too tall each side. I'd stuff a single 9/16" tall piece right in the middle of the middle port on each side. In our builds this turns out to be the only place on the box with significant resonance. So you have the opportunity to turn a mistake to your advantage.
dave
Steve,
McShane has 0.22 μF./600 WVDC 716P film and foil Orange Drops for $2.45 each. Betcha Jim charges less for shipping too.
There is more than 1 way to "jump" in replacing the multi-section can capacitor. Notice the Octal socket next to the rectifier's "hole". Undoubtedly, an umbilical from the tuner/control chassis connected there. You can knock that socket out and use the opening for another can capacitor, if necessary. For instance, McShane shows a $19.75 clamp mount 500 WVDC 40/20/20/20 part. $1.50 buys the requisite clamp. Add a 20 μF. 'lytic under the deck and you are good to go.
The OEM 100 μF. part is, without question, a 'lytic.
BTW, under NO circumstances should the 1st filter cap. after the rectifier exceed 40 μF. Vacuum rectifiers will destructively arc over at turn on, should an overly large capacitance be present.
McShane has 0.22 μF./600 WVDC 716P film and foil Orange Drops for $2.45 each. Betcha Jim charges less for shipping too.
There is more than 1 way to "jump" in replacing the multi-section can capacitor. Notice the Octal socket next to the rectifier's "hole". Undoubtedly, an umbilical from the tuner/control chassis connected there. You can knock that socket out and use the opening for another can capacitor, if necessary. For instance, McShane shows a $19.75 clamp mount 500 WVDC 40/20/20/20 part. $1.50 buys the requisite clamp. Add a 20 μF. 'lytic under the deck and you are good to go.
The OEM 100 μF. part is, without question, a 'lytic.
BTW, under NO circumstances should the 1st filter cap. after the rectifier exceed 40 μF. Vacuum rectifiers will destructively arc over at turn on, should an overly large capacitance be present.
Eli Duttman said:
FWIW, I'd put the NFB on a nice toggle switch, as I did in my EC variant. I only listened to it for a few hours (before leaving home for a few weeks). Without feedback mine sounds sloppier, but maybe nicer in the mids. If you ever plan to use the EC with some wimpier sources (like an Ipod), you need all the gain you can get (the EC was optimized for the standard CD player 2V of output), so the ability to switch the feedback off could make all the difference when trying to achieve a decent output level when connected to a device that outputs less than a volt.
I don't have a great deal of tube experience, but I have heard a fair number of amps in my time. The EC is easily the best reasonably priced thing I've heard, and I can't recommend it highly enough.
pj
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