Bottlehead Forum
General Category => General Discussion => Topic started by: Alonzo on July 03, 2012, 08:53:06 PM
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Got some time off for the holiday, so I thought I'd document a weekend project.
Start with a Single (45) schematic and parts list, add a fairly full parts bin and you get a junk'd full breadboard that HUMMS.
(http://temp board.jpg)
Today the little brown truck arrived and brought in a top plate and base from the good elves north of me.
(http://chassis bare.jpg)
Now how to squeeze this into this....over the weekend
(http://side by side.jpg)
Also have to deal with the hummmmmmm......
Going bare on the chassis, can't decide on a good color. The base will be varnished with some gloss polyu I have on hand.
Wish me luck; I'll be adding notes and pictures to show the progress.
Alonzo
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I could do that ... only my wires would originate and end up at random points and it wouldnt work ;D I envy you guys who understand this stuff enough to be able to put something together from old parts or scratch and make it work. I have fixed a few vintage tube amps and such that didnt work or didnt work right but never considered that it was anything much more than luck. Plus I had online help with schematics, parts and general advice. I guess I shouldnt complain as most people couldnt even do that and I still got the satisfaction of getting it working and enjoying afterward. Im definitely more of a kit guy, not a from scratch builder. Im just an all around jack of all trades, master of none ... except maybe one, I was good at my job ;)
Happy 4th and please update, I enjoy seeing this stuff.
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Alonzo,
You always crack me up with your use of things unintended for DIY. The outlet cover plate with hole shrinkers is what I mean in this case.
It looks like you will need a shoe horn to get all that into the FP III chassis/base. Maybe some Crisco?
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Never thought of using an outlet cover plate as a tube mount, very creative! Almost looks like something Decware would make.
Cheers,
Shawn
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OOOOO Decware. I have dealt with some of their stuff. Some I liked, some I sold. But honestly, I still miss a pair of mono amps. that they made many years ago. Good looking, solidly built, and I haven't had that kind of luck since. I will, however, finally be diving into a simple Quickie kit. I have no doubt that it will sound better than expected. Simple things usually do. Now, where did I put my stash of brass outlet plates?
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Hope everyone had a safe and Happy Independence Day!!!
Didn't get much done, too much of the "adult lemonade" and burgers to attempt anything more than using a screwdriver. I have the stereomour chassis and thought I'd somewhat mimic the layout but after putting parts in, saw that it wouldn't work so most of the tag boards you see in the picture are being removed tonight. Since I'm making this up as I go, I'm going to build out the power supply then one channel, hopefully working out the layout bugs and adding the second side.
Laudanum, I'm a kit guy myself. I prefer them to scratch builds but sometimes the money doesn't work out for buying a kit so you do what you can. I'll be leaning heavily on the community here for help, I try to keep a simple build, not get too over my head but learn something new each time. And I subscribe to Grainger's motto "If it sounds good to you then eff everybody else" (or something like that ;D.) Whenever I think different I visit an audio retailer down the street, listen to his high end gear and smile, I"m more satisfied in building it myself and having it sound good and using the extra money on a good steak, cigar and single malt.
I join you in the JOAT club, the Navy made me that way.
Yesterday's progress pics attached. So far so good but this isn't the hard part...
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Alonzo ... JOAT has served me well with lots of things over the years but especially because it has kept the wife happy with those honey-do's and saved a boat load of money in the process. ;)
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Lost an update somewhere in the ether...
So far not much progress, but I have a great reason why. Recieved my 6th grandchild, Bennet Elias Bradford into the fold so I'm having a ton of fun with the new baby to visit.
I did some cleanup and mounting of parts yesterday, got the power supply transformer on some offsets, added the chokes (4) and output transformers,etc. Now I have to plan out the ground plane and the layout for a CLCRC filter on the tag board.
Anyone have experience with Sprague Atom capacitors, I have 2 and wonder is it worth the effort to try to fit them in the power supply? Will have some time next week, hope to get this to power testing by Friday.
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Alonzo,
Congratulations on both the birth of a grandchild and the impending birth of the amp.
Sometimes life just gets in the way of builds.
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Losing post somewhere when the pictures are too big. Here's the latest on the project, 45 amp in a Stereomour dress. Got alot finished but it's not complete, theres some imbalance between the channels and I need to track down and eliminate some hum.
Some things left to do: replace the chokes with BCP-15's, new power resistors of the correct value, possibly a fan underneath (this amp runs hot, touchable but definitely warm), oil caps to replace the big Sprague ones in the power supply, clean up the chassis some and find some vintage knobs, maybe upgrade the Solen's to Obliggatos, maybe replace the power transformer, maybe a Nixie tube indicator or as a meter.
It has about 40 hours on it, I'm reserving sonic judgement until it's over 100.
Here's some pics, please forgive the wiring mess, I starts out neat in my head then ends up like my desk...
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Under the hood...
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Alonzo,
Nice work. Very Bottlehead.
In the FAQ Thread (http://bottlehead.com/smf/index.php/topic,2408.0.html) in my corner there are instructions on how to post pictures from a hosting site.
Can you put the old late chokes into the power supply like in the old Paramour upgrade? I'd hate to waste good iron that can improve the power supply. It looks like there is iron below the plate already.
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Thanks, it's got a C-7X choke in the power supply. It's a CLCRC, 100uf/10Hy/100uf/1.5K/82uf, and there's a .01/630v across the incoming power (don't know if it does any good, had an extra from a Foreplay mod to use). The plate chokes and outputs are under the top plate, I've ordered new chokes from Mike, just waiting for them to show up. Going to add a right angle power cord as soon as that comes in also.
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Somewhere I have a link to a 90 degree IEC female. Yup:
http://www.mcmelectronics.com/product/28-11500
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Alonzo,
that standard film cap across the incoming line is potentially dangerous -- typical coupling caps are not rated for AC power line use. If you're going to do that you should find some X1 rated caps These have a guaranteed failure mode, unlike a standard cap which does not.
Are you using the exo-45s you got from me?
-- Jim
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coming in late on this but I also have aspirations to read a schematic and build a kit from scratch! I find that very cool. I give credit to Bottlehead for the intro. Before that I didnt know a triode from pentode. I know it will probably happen at some stage, but for now, I'm a practical audiophile, and if it aint broken I'm not fixing it!
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Jim, what's an X1 rating? I looked up the data sheet for the cap I'm using and it states the cap is good up to 250v AC at 60Hz. It's a Vishay MKP 1840. Yes, I'm using the EXO-45 I got from you, they aren't broken in yet but will be soon.
While I was under checking the cap, swapped out the Sprague and changed out some resistors. Trying to decide whether to connect the heater center taps to ground, if it'll make a difference in the hum.
Grainger, thanks for the link. I ordered a bottlehead cord kit to try.
New pics...
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Alonzo,
OOoooo Lots of caps and iron. Makes for a sweet sounding amp.
Do I see a FP 2 in the background, upper left, in the background of the second picture?
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Grainger,
Good eye!! That Foreplay wasn't getting any use since I put Quickies in my system. It is now the sacrificial lamb for an idea for a Foreplay with switchable inputs and outputs, I want something I can switch between my 3 sources and 3 amps and 3 sets of speakers plus a sub to each when needed. I used the Foreplay chassis to get a copper top made, the base to house one of my Quickies. So far that's as far as I've got, I keep thinking adding tubes to a switch box would be overkill since I already have preamps in the setup. But I've got to do something with all the 12AU7's I have!!!!!
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Hey Grainger,
What do you know about Grid chokes? I did a search but the info was confusing, cycling between different amps, different values, etc. so I thought I'd ask. Did you ever put grid chokes on your paramours? If so where? What kind of improvement did you get?
Thanks!!!
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hmmm, I don't know Jim, I've used a 600v 2uF Auricap across the main of my Mac C22 with great sucess. And it was the designer of the capacitor and engineer for Auricap that suggested it. Years later there has been no problems.
Aaron
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Alonzo,
I know only one thing about a grid choke. It replaces a resistor from grid (or outer lead of grid stopper resistor) to ground. I never put them in my Paramours. It is pretty full already. Take a look:
http://www.bottlehead.com/smf/index.php/topic,1185.0.html
I pretty much got nothing!
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Grid chokes are a double edged sword. They can give a really great improvement in the sense of dynamics, but they are susceptible to hum pickup. So they don't work in every setup. I would suggest connecting them and rotating and otherwise moving them around for lowest noise pickup before committing to a location on the chassis.
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Thanks Doc,
Is this a spot where higher value is better? Mike's BCP-16's or equivalent? I have some room to the front of my chassis, will long leads also pick up hum or is it a function of the windings in a magnetic field?
Grainger, that definitely is a blivit. You do need a taller base, there's always more iron, bigger caps....
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Sorry folks -- still in the midst of a sea of boxes, unpacking and dealing with a wrenched back on top of it all.
Here's a pretty basic primer on line rated caps that hits most of the high points:
http://www.justradios.com/safetytips.html
I hope that gives folks enough info to make a decision on whether they want to continue with their current caps or switch to something a bit more safe. It's not that your typical poly film cap won't work across the line, it is a question of when and how it will fail -- especially those of you who live in places where electrical storms are frequent and intense, or nearer to power plants and large substations where large voltage spikes can happen.
Me, I'd just do it for peace of mind. :D
Thanks, and happy reading,
Jim
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Thanks Jim, interesting read. Even though I'm not the safest person in the world, I wouldn't want to start any fires. I took a couple of pages of reading to find my caps weren't recommended for "across the line" applications, they really should put the safety information in the front. Luckily Vishay makes other caps that will fit my situation.
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Alonzo,
No problem -- it's just one of those things not many folks know or talk about but it is good practice especially for us diy types.
I will probably try this on whatever amp ends up at my bedside table as the only nearby electrical outlet also has hardwired into it, the two dimmable halogen reading lights my wife had installed on each side of the bed. I have very little room to work with here so I'm going to have to come up with a very clever, compact outlet strip and filter setup for my headphone rig. I've got some ideas but no shop in place to make it happen yet.
-- Jim
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Alonzo - count me as a grid choke fan! I have them in my Quickie now. Been back and forth between Paul's very well designed CCS and the chokes, and I think the chokes will stay in this time. I think it may because I listen to digital. If you are analog then the CCS may be 'cleaner' and better.
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I have a pair of BCP-16's in my SR-45. I like them a lot in this amp. added a good bit of Dynamics...John
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The chokes used in a Quickie would be plate chokes, not grid chokes.
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Doc - thanks for the correction on that! Granger had me sit in the corner with my 'dunce' cap on for an hour... then I was forgiven. Boy if life was only that easy!
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Eric,
I've been in that corner before...I think everyone visits there now and then.
John, what are you playing your SR-45 into, I"m playing my 45 into horns, so I"m trying to determine what will improve, I have a hard time defining "dynamics". Did the sound stage expand, or more depth to voices and instruments? These chokes are probably a month or so away, I've got to get onto Mike's build list, in the meantime I'm adding BCP-15s hopefully soon.
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I thought it was my corner.
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"I thought it was my corner."
Yea, we are the guys that come over and drink all of your beer and eat all your food 8)...John
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Alonzo, I use the SR-45 mostly with Hornshoppe horns. The grid chokes Give more of a sense of attack and make the amp seem more powerful and alive. It did not change the tone much. The sound stage did not change in size so much as the space it conveys seems more solid and real. I can hear more of the room in which the recording was made...John
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"IN THIS CORNNNER, IS JAHNNN, THE SOLDER KING(SHOUTING/APPLAUSE). AND, IN THIS CORNER,-, THE RETURNING-BURNNNN CHAMP! GGGRAINGER! THE BOTTLEHEAD SMASHHHER! ( BOOO! 'YER A BUM! {SORRY, IT'S NOT YER HOME TOWN}). JUDGING TONIGHT WILL BE KKKROWWWW...."I DON'T WANNA SEE ANY COLD JOINTS-HOT LEADS OR BURNING BELOW THE BELT. GENTLEMEN, START YOUR IRONS."
Somebody make it stop.....
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LOL!!! Greg - well done!
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I thought I was the Corner Sitting Champ. Just ask my Mom.
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John,
My Frugel horns are a similar design so it seems that the chokes will be good for me also. Will give it a try once I have chokes and have fixed the amp.
I've committed a triple sin, I've killed 3 1940 45 tubes for some reason I can't fathom. While playing the amp and breaking in, about 45 - 1 hour in, one channel will die. I thought it was a bad solder joint opening when heated so, I re-wet pins 1 and 4, looked for shorts and started again. About an hour or so later, tube #2 didn't work. So me, being dumb, took a layer apart to check solder joints, checked voltages on the heaters, plugged in a new tube and a short time later, another tube bites the dust.
So after 3 tube failures I decide to take the amp down for repairs but I can't see any thing wrong. I measure 2.9 volts AC on the heaters, the transformer is rated for 5v CT 3A, I'm running the 45 heaters in series with no CT, each measures out at 2.9 volts.
This has happened on the same side, the side extended from the heater wiring. I'm thinking of replacing the wiring due to a heat induced short, just to see if that's it, but I don't see any obvious causes. Does anyone have any ideas?? Oh yeah, tested it with some 2a3's and they played fine...
I'm at a loss, please help...
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2.9V is a 16% overvoltage. That is quite high, most of the old texts say the filament voltage should stay within +/- 5%, i.e., 2.375 to 2.625V. So that might be at least part of the problem. However, if it keeps happening on only one channel it might be that something else that is isolated to that side is causing the problem. That fact that it doesn't happen for 45 minutes tends to indicate that it is either a thermal issue or maybe it is in fact that the tubes just tend to die after 45 minutes from the filament overvoltage. I'd suggest using a resistor in the filament supply to get the voltage closer to 2.5V and using an expendable tube like a worn 45 to see if it holds up over time.
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As it happens my SR-45 uses a single 5V Hammond filament transformer. When I built it the 2.5v were on intergalactic back order. What I did was to cut the tape on the bobbin and separate the center tap so I have two 2.5V windings on one core and I have very close to 2.5 VAC at the 45.
If your 2A3's survive, could it be that your plate voltage and/or current are too high?...John
edit, I just reread your post. I think it is a bad idea to run the 45 filaments in series
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I agree with John -- the filaments in series caused me some wonder as well. With dhts, I've only seen that in push-pull pairs.
-- Jim
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I think I mis-spoke, actually mis-typed ;D The heaters are daisy chained but electrically parallel ( I think). The twisted heater wires go to pins 1 and 4 of the right tube, another twisted set goes from R1R4 to L1L4, R1 is connected to L1 and R4 is connected to L4. I always get serial and parallel meaning mixed up. I think this is parallel wiring.
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Now I am getting confused. Not from what you mis-typed, but from what is going on inside my mind.
The cathodes are in the signal path. With a common power supply that ties the two cathodes together somehow. My head hurts right now, woke up with a headache. I'll have to think about this. If my thought is right all stereo amps with DHT tubes would have to have dual heater supplies. I'm thinking that this isn't right. But my head hurts.
More later, less sooner.
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Wait - the filaments are in parallel, so they draw 3 amps at 2.5 volts, and you are feeding them from a 5 volt/3amp winding? And you only see 2.9 volts? There is more than one thing wrong here. The transformer should happily make 5 volts at a 3 amp draw, and the 45s should die quite rapidly with 5 volts on the 2.5v filament.
Perhaps you are using just half the 5vCT winding, and ignoring one of the end leads? And you power line might be much higher than the transformer was designed for? Those things together might make the moderately excessive voltage. If you are really getting only 2.9 volts from a 5v winding there is some other problem.
If the filaments are not independently biased, you may have one tube that is hogging the current, leading to excessive dissipation and even cathode stripping.
Once you get the power supplies straightened out, it is possible the cathodes can be re-formed and there may be some life left in those "dead" 45s. No way to be sure, of course!
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I have a breadboard DRD amp set up that will run any 4 pin tube. Once I was changing from 300B to 45. I was so focused on dialing in the B+ and driver voltage, I forgot to set the filament to 2.5V. Needless to say it didn't last very long...John
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John,
Now that I have to pay more attention to these things myself, how much different was the old filament voltage setting as compared to the new? I am working with various tubes and power supplies, and had better watch myself! Musical Fidelity makes a buffer amp that I am presently working with, but there isn't enough information for a guy like me to really go to far with it. Not even a schematic as far as I know.
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How do they propose that you assemble it without any instructions?
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I had it set for 5VAC for the 300B.
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Well, actually, the Musical Fidelity is a complete/assembled product that some like to hot rod. Of course, you can buy a kit for changing out caps, diodes, and wiring, but, I wanted more. A power supply, for example in addition to the rest of the upgrades just made good sense. So, I am waddling through this stuff with one hand behind my back. I'm gettin there, but not like others who probably have a better understanding of the circuit in the first place. One way to start out in a better position was to buy an additional unit, and measure the voltages per normal operation. Too many fires on the brand, err, brands on the iron, or something like that. I have got to get some of this stuff out of the way...one, at , a , tiem. errr, thyme.
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Started to poke around in my amp, check resistances and voltages and do a connection by connection comparison (since one side worked and the other didn't) to find my mistake. Haven't found anything different yet but I did find some wiring showing burned insulation (see pic). This is the wire connecting the the power supply choke to the dropping 1.3K 10W resistor. The cap at this connection looks fine.
So I'm off to my parts bin, looks like I may have 2 or more problems, not just an out of spec heater current/voltage.
Sorry for the flash glare, you can see the burned red wire center of the picture.
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Looks to me like the wire insulation is just getting fried because that big metal resistor is cooking it. It's probably PVC and replacing it with Teflon insulated wire is probably the best solution. If it's already Teflon wire - yeow - that sucker is getting really hot!
All that said, if this is a single high voltage supply it's not likely that that melted insulation is causing a problem on only one channel.
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Finding out more and more....replacing all the power supply wiring with teflon insulated wire. The C-7 choke on the nonworking side reads 151 ohms, 247 for the working side so I'll be replacing that choke also. Lots to do this weekend...
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Pinging Paul J., pinging Paul J.,
You mentioned back a couple of responses ago that my 45 tubes cathodes may be re-formed. While I wait on filament transformers and plate chokes to be delivered, is there a method of bringing these tubes back to life?
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Don't do anything until you have the correct filament voltage. Then you can run the tubes in the amp, monitoring the plate current, and see whether the current returns after some burning in. If it doesn't come back in 50-100 hours then they are probably well and truly dead.
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Got my filaments transformers in the mail today (yaaaaay!!) so since the chokes are still out there somewhere, I'm going to install the filaments and work on burning in and hopefully reforming the cathodes on my blown 45's. Now the question is; is it an advantage to install a switch to turn these on first for normal operation? I don't want to just run the filaments ( I think) for the re-forming but it should be better to warm them for normal operation.
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Yes, re-forming requires both correct filament power and some plate current through the tube.
And yes, warming the filament before applying high voltage will normally extend the life of a tube. There is little consensus about how much difference it makes - it's not huge, or everyone would agree - but I think there are some old statistics from the fifties to support the theoretical notion.
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I'm starting my rebuild of the amps power supply and I came across an item I'd like some opinion on, actually a couple of items. I'm changing the PS layout and form, going to a full wave rectifier with UF4007's and I thought about adding another LC phase to the filters. I have some Hammond 155J chokes (1K ohms 15H 30ma) that I thought of using. Since I have to add a 2K resistor to drop voltage, why not use a choke/cap and a smaller resistor in it's place. When I run it in PSUD the numbers are pretty much the same, would there be a big sonic difference?
BCP-15 have arrived so in they go...
Also have some MCaps (47uF 400VDC), would they be wasted as PS caps at the last cap of the PS filter before the BPC-15?
Pic's attached of the new parts...and of the PSUD scenarios
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Finally think I'm done (at least with the mechanical portions, it still could use some "beautifying" and a right angle power cord. Added plate and grid chokes, increased the value on the cathode bypass and the coupling cap. Gonna let it burn in for 6-7 months before I look at it again. A better power transformer is needed and to hopefully get rid of the filament transformers.
It's playing the local jazz radio station now, sounds pretty good, the real test is tomorrow hooked to the "regular" system of turntable=>seduction=>quickie=>horns. Hopefully there's not much hum, right now I can't hear any at my listening chair.
Some pics of the "blivit".
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Alonzo,
Congratulations! That re-desines the long weekend if you ask me :-). Looking forward to your impressions in the regular system.
-- Jim
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Alonzo,
You need a bigger chassis plate!
-PB
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Jim,
Take this with a grain of salt, it may be proud papa syndrome but I think it's a definite improvement, like >50% than my other DIY effort. The quality of iron (all Magnequest) and some boutique resistors definitely make a difference. I haven't heard any of Mike's nickel irons but the M4 outputs and chokes seem excellent. And I haven't started tube rolling yet. Voices are clear and all the mids sound distinct. Bass is full (thats the best I can describe it, my horns don't go very deep but I don't see the need for my sub yet, not on classical music, I may later once I start into my jazz and blues collection.
Oh, and it's alot louder than I thought it would be.
Now I have whittle about 20 45's down to a good 4 to 6 and about double the amount of 12AT7's to a resonable amount of backups. And maybe for Christmas I can squeeze in a pair of 45 mesh plates.
Paul,
Definitely, but I'm terrible on layout and such. It was much easier on me to make it fit onto a pre-cut chassis plate. Also I just wanted to see if I could do it. Even if it would've come out terrible, I enjoyed building it.