Barley Nectar
688 posts
Mar 02, 2015
10:08 AM
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Bolted everything in that I have currently. Ordered remainder of parts from Mouser just now. Rooted thru my tube stash and came up with these. Nice Glass here! The Sylvania 6L6's are used but test very close and strong. We won't know the real story till we get them heated up. I do have other options. No components soldered in yet. I'll get the stuff from Mouser probably Wednesday, they are FAST! Hope to have this done by week end. Here's the chassis , no pots yet...BN
Last Edited by Barley Nectar on Mar 02, 2015 10:09 AM
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Barley Nectar
689 posts
Mar 02, 2015
10:20 AM
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blueswannabe, WOW, that's crazy! That amp probably needs rebuilt as well. I probably got 100 bucks in this project. Not counting the cab. A lot of the stuff is scrounge for cheep! Rock-N-Roll
Last Edited by Barley Nectar on Mar 02, 2015 10:21 AM
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Mojokane
789 posts
Mar 02, 2015
7:30 PM
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Wow!!! NICE, coming together fast!
Is the 7F7 less gain?
Thanks, I searched web with little results.
My MA17 is really hot...with amazing tone (worth keeping in the arsenal),and the venue I play is too small. I am happy with what I got, but I ran across a 7F7...what is the dif?
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Why is it that we all just can't get along?<
Last Edited by Mojokane on Mar 02, 2015 7:34 PM
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blueswannabe
553 posts
Mar 02, 2015
8:05 PM
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$740 is crazy money for a such an old amp. It was in great condition, however, but still too much. Your build will hopefully prove the point that you can make it yourself and get the same tone from the amp. Sorry to put the pressure on but I would like to see how it measures up to a stock amp.
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Barley Nectar
692 posts
Mar 02, 2015
9:36 PM
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That would be an interesting comparison but I don't have the stock amp. This will not sound the "Same" but two matching, vintage Deluxe Reverbs will not sound the same either. Too many variables. I will be very happy with this sounding good.
This amp is a hybrid of two circuits. It uses the 6SJ7 from the Masco ME-18 and the 6SL7 from the Masco MA-17. No choke in the power supply. Also using 47,22,22,10,10uF for the filters. This is quite a bit stiffer then the original amps. There is also the fact that the transformers are not OEM Masco. My PT is somewhat higher voltage at 350-0-350. I may adjust the droping R's for the preamp if needed.
Some folks mod their amps endlessly. I chose to let the amp be itself and learn to work with it's strong points. Don't get me wrong, I do mod some amps but I also return them back to stock at times, mainly because I liked them better the way they were. Ya just never know but it's all fun! ...BN
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blueswannabe
554 posts
Mar 03, 2015
8:45 PM
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I have a VHT with no mod to the circuit. Sounds great! ALso have a masco 17N which is mostly stock circuit with several small chnages (unsoldered the feebback resistor, and increased a couple tone caps, left the power filtering values the same). And that sounds great! I have gigged with it a few times playing through my VHT, using it as a cab. I agree that you have to play to the amps strengths and just vary your technique.
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Barley Nectar
702 posts
Mar 08, 2015
4:48 PM
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Update: Have the chassis half wired. Still waiting on parts. Snail Mail, LOL.......................
I decided to power up the PT and check the OT for noise with the scope. This is a check for magnetic coupling between the transformers. No wires connected. Was getting .7V Peek to Peek across the OT primary. I found that by turning the OT on it's side, long side down and staying on the PT centerline. I was able to reduce the OT primary induction to 32mV peak to peak. That is a HUGE difference. SO, I subbed out the thru chassis OT (pictured) with a surface mount unit of like size and spec. This setup will be much quieter! Kinda glad the parts are slow commin. Gives me time to think...BN
Last Edited by Barley Nectar on Mar 08, 2015 11:58 PM
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Barley Nectar
708 posts
Mar 16, 2015
4:39 PM
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Parts finally arrived last Thursday. Hit it pretty hard past weekend. Got the board loaded, wired, and installed in the chassis. All that is left is to land the flying leads from the board to the tube sockets. Getting pretty tight space wise. Lookin good though. Can not post pics due to computer problems. Allways something...BN
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blueswannabe
557 posts
Mar 20, 2015
7:04 PM
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@Barley, what's happening?
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arnenym
344 posts
Mar 21, 2015
3:53 AM
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I love it! Be careful. Isolate or ground the metal cab in the amp chassie.
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Barley Nectar
711 posts
Mar 21, 2015
4:13 AM
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OK, wiring was completed Tuesday night. Will power up today. I hit these new builds with 12VAC first. 10% of operating voltage, then look at circuit V's. Everything should be 10% of suspected operating V. To do this you must insert an SS rectifier because tube rectifiers need about 60% voltage to conduct. Variac, current limiter, GFCI, and metering are built into my home made power supply. Pretty handy device.
Here are a few pics prior to compleation. Banjo is helping.
Chassis is well grounded Arne, thanks for your safety concerns.
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Barley Nectar
712 posts
Mar 21, 2015
4:23 AM
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Here's a shot of the "Lab" in use. Power supply is on right. All sitting on reperposed organ benches. Great hobby...BN
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blueswannabe
558 posts
Mar 21, 2015
3:50 PM
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looks great, as does your work bench! can't wait to hear how she sounds!
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Barley Nectar
713 posts
Mar 21, 2015
5:25 PM
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Made from a drywall stud, "The Stud" lives! Up and running after installing that one wire I left out...This thing is powerful! Have not checked the wattage yet. It seems a bit gainy. Tone control works well. Power tubes idling at about 55%. Everything looks good and it is pretty quiet, even when cranked. Time to tweek this baby in. V1 (6SJ7) plate V needs lowered and screen V needs raised to reduce gain. Will add an external speaker jack. My first impression is that this will crunch up nicely with some space to breath. Vintage Tone!...BN
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blueswannabe
559 posts
Mar 26, 2015
5:01 PM
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looks great, can we get a sound clip.
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Barley Nectar
720 posts
Mar 27, 2015
9:44 AM
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It blew up! LOL. Had it cooking on the bench for about 3 hrs and the PT blew. This was a no name salvage unit. Funny thing was, it did not get real hot??. Anyhoo, I went to the garage and found a Hammond organ PT that is 75% thicker and put that in. Amp is now making 14W clean, 30W max. Took the amp to a jam last night. I am quite please with the initial results, as were the other musicians. I found that the tone control effects the volume quite a bit. Brighter is louder. Not a problem with a mic VC. This was very evident on the scope during checkout also. It is still rather gainy but not out of control. Arne has suggested running the 6SJ7 cathode biased. Will probably try this.
Sound clip? I have a Zoom H2 here that has a few shows on it. Don't know how to get the stuff into my computer. I did buy a card reader but don't know??? I'm not great with computers...BN
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HawkeyeKane
2751 posts
Mar 27, 2015
10:22 AM
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Hey Goose...sent you an email earlier with something you might like. ;-)
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Hawkeye Kane - Hipbone Sam
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Barley Nectar
721 posts
Mar 27, 2015
9:51 PM
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http://www.ebay.com/itm/251886327435
Another great harp amp, homosote cab and all it's glorious cheepness. Lectrolab, R600c. I'm figuring that the "c" suffix means EL84 power tubes. "b" is for 6V6. I have the R500c, no Trem. Put in a real wood baffle and Jensen P12Q as the "R" was blown. The circuit is freshened but otherwise stock. Awsome tone and very light weight. Don't sit on these amps! They will crush!
I drove to Cleveland Wednesday (222 mls) to pick up another rare '50's amp. Craigs list find. Could not pass it up for the price. Stay tuned for pics...BN
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Bilzharp
46 posts
Mar 28, 2015
7:49 AM
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I'm enjoying your build thread. Yeah, that first PT looked a bit small to power 6L6s. Admittedly, I'm no expert but that looked more like the size for a pair of 6V6s or a single end amp. Sounds like you've got that squared away now. Your original OT looked more substantial to me than the one you have now. Could you have addressed the hum problem by rotating the original OT 90 degrees in the horizontal plane instead of replacing it with one that rotated it in the vertical? I've always read that the PT and OT should be oriented with the windings at right angles to reduce hum. Can't wait to see what amp you drove 200 miles for!
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Barley Nectar
722 posts
Mar 28, 2015
8:48 AM
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Bliz, yes you are right. That probably was a 6V6 size PT. I label them when I pull them from old gear but that one came to me solo. It is difficult to determine actual VA capacity of salvage iron. The blown one fooled me because it did not get unreasonably hot. Just warm?
The replacement OT is the exact same size as the first one. My induction testing showed that the final choice of stack orientation is the quietest possible with the space available. The OT was turned every which way. I feel that my test procedure was pretty accurate.
I am not a expert by any means. This is my first shot at building a chassis from scratch. In the past, transformer orientation and selection was spelled out for me. By posting my success and failures, my hope is that others will learn. This is ancient technology but fascinating. Plus this stuff sounds and looks so cool...BN
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Bilzharp
47 posts
Mar 29, 2015
5:32 AM
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I kind of figured I wasn't telling you anything you hadn't already tried. In fact, I'm inspired to make some attempts at hum-reduction in a rebuild I did last year. I converted an old Silvertone from a field coil to ceramic speaker and I think I need to try a different location for the OT.
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Barley Nectar
723 posts
Mar 29, 2015
7:11 AM
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First thing, make sure it is not a tube causing the hum. Non matched power tubes are suspecious.Try reversing the AC line polarity at the PT primary. I found that this made a difference of aprox 10mV of induced noise at the OT. Also try relocating the ground wire from the plug to the chassis. (Green Wire) I have found that the line ground should be tied to a PT mounting bolt all by itself, not with any other circuit/transformer grounds. If you are familiar with hot chassis safety procedures, try chopsticking circuit wiring while the amp is on and tied to a speaker so you can hear the results.Remember, these amps contain high voltages that WILL KILL YOU, even when turned off!! Did you use a choke or a resistor as a sub for the speaker FC? A properly sized choke may be quieter if the old FC was part of the power supply filtering. If your heater secondary winding in the PT does not have a center tap tied to the chassis, you may need a virtual center tap using two 100 ohm R's to ground. Hum can be a bitch to get rid of but you learn a lot chasing it...Good luck Bliz...BN
Last Edited by Barley Nectar on Mar 29, 2015 7:20 AM
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Barley Nectar
735 posts
Apr 03, 2015
7:39 AM
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OK, still tweeking this amp. I noticed some hum when I was at the jam last week. Hummed pretty loud when amp is cranked. This seems to be typical of the 6SJ7. Also amp is too gainy.
After poking around, looking for the hummer, two 6V lantern batteries in parallel, were subbed in to feed the tube heaters. Hum was totally gone! Next, tried this on just V1 (6SJ7) hum still gone. So, I decided to try and feed V1 heater with DC. Research led me to the Marshall Studio 15 (4001) circuit. This amp uses a bridge rectifier, E cap, and a virtual center tap to make DC to feed the heater on the first 12AX7. Perfect! The PT filament secondary winding must have a center tap of some sort, for this to work. I built a small circuit board and installed the DC supply. Amp is now very quiet, even when dimed!
Now for some gain reduction. First the 6L6 cathode R was increased from 180 ohm to 200 ohm. This will cool down the power tubes some and should help with FB. My buddy Arnenym has a lot of experience with the 6SJ7 in V1. He suggested changing the input topology from grid leak, to cathode bias. His setup is 68K input R with 5M R to gnd. 1K cathode resistor. All else stays the same. I did this and found that the amp is much more controlable, volume/feedback wise. Thanks Arne...
Taking the Masco build out tonight, so we shall see how she sounds now...Goose
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HawkeyeKane
2756 posts
Apr 03, 2015
12:16 PM
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Go get em Goose!!!
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Hawkeye Kane - Hipbone Sam
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pharpo
772 posts
Apr 04, 2015
9:00 AM
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I am looking at a MA 17N is that the same as the MA 17. Also looking at a Bogen CHA 33. Does anyone have any experience with Bogens ?
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Procrastinator Emeritus
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Barley Nectar
736 posts
Apr 04, 2015
9:29 AM
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I would say that the Masco MA-17/ME-18 are highly regarded, by the harmonica world, for good reason! Played it out last night with some fellows that I have not seen in 20 yrs. Mostly country with a little old rock thrown in. Not loud. The Masco was defiantly a hit. One fellow said Wow, what is that big deep sound your making! TONE! I have a bunch of amps here, some stock, some modded, some home built. I have NOTHING that sounds like this baby. Huge Chicago sound! The mods worked out perfectly, no FB problems, no hum. Thanks Arne. Plenty loud, I took a 1x10 extention cab but did not need it. I'm really happy with this amp! Final pics coming. Oh ya, pics of the new/old mystery amp coming also... Thanks for the input on this project folks, hope you enjoyed the show...BN
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Barley Nectar
737 posts
Apr 04, 2015
10:01 AM
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pharpo, MA-17n is a different amp. Has one more preamp tube, a 6sc7. Probably too much gain as is. I do have a stock Bogen CHA 33 here. It is not really a great harp amp as is. Most of these old amps need totally rebuilt and modded to be good for harmonica. Unless your into this, those old amps are not a good investment. Tech's cost a fortune and most don't know harp tone/mods. I feel you will be better off with a harp specific amp by one of the major builders discussed here on MBH. Or one of the few recocnized harp friendly amps such as a RI Bassman. Even the Bassman could stand a few tweeks. JMO of course. Good luck to ya...BN
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KC69
445 posts
Apr 04, 2015
11:54 AM
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I could probably be talked out of my 1952, Masco MU-5. I just don't play it often. Rick Beets could tell you more about it. I bought it from him, off the forum, last year.
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And I Thank You !!
KCz
Backwoodz
Bluz
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pharpo
773 posts
Apr 04, 2015
1:34 PM
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Thanks BN....I am familiar with all the harp amp builders. While I'm sure they are worth it, I'm not able to plunk down 1500-2000 for an amp. I have amps that work fine....but you know I have the affliction GAS - "Gear Acquisition Syndrome" and have always been intrigued by the Masco's. I may try one of Ricks Memphis Mini's down the road....they seem to be pretty affordable. Right now I am using a modded 65 Ampeg Rocket that screams !
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Procrastinator Emeritus
Last Edited by pharpo on Apr 04, 2015 1:36 PM
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Bilzharp
49 posts
Apr 05, 2015
8:01 AM
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"A properly sized choke may be quieter if the old FC was part of the power supply filtering. If your heater secondary winding in the PT does not have a center tap tied to the chassis, you may need a virtual center tap using two 100 ohm R's to ground. Hum can be a bitch to get rid of but you learn a lot chasing it...Good luck Bliz...BN"
Thanks for the pointers on hum reduction. I tried another pair of output tubes, swapping the Xfmr primary wires, putting the 100ohm resistors in the heater circuit, reorienting the OT, adding another 20ufd to the filters, all to no avail. When I replaced the speaker I subbed a 680 ohm 10W resistor for the original field coil. I think your suggestion about using using a choke instead of a resistor may have merit. Any suggestions on what choke to use and where to get it? Mouser? I think I remember the original field coil measuring around 650 ohms DC resistance. I may have to try something like your lantern battery trick too. Where did you find the regulator circuit that you wound up using for your V1 heater?
Glad to hear that your amp is working out so well. Bet that little lunchbox sounds as good as it looks!
Last Edited by Bilzharp on Apr 05, 2015 8:04 AM
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Barley Nectar
743 posts
Apr 05, 2015
7:28 PM
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Bliz, unfortunatly I don't know how to size a choke. There may be a rule of thumb out there but I don't know. The DC supply for V1 came from a Marshall schematic. Amp model is 4001, Studio 15. That amp uses a simple bridge rectifier circuit to feed the filament on V1. The bridge is a A005 type but I used 4, IN4007's and a 3300uF 16V ecap because I had them in stock. Makes sense for Marshall to do this as it is in a "Studio" amp. It made a huge difference in my build but I knew what was causing the hum before the DC supply was added. That is the tricky part, finding the source of the hum. I do have a hummer here that I never could get straightened out. Luckly you can't hear it in a noisy bar but it would not work for recording. You do know about wire orientation I hope. Signal wires need to cross power wires at right angles or you get inductive coupling. Never run signal wires parallel and close to power wires, especially AC power. The AC line and the heater wires are the most notorious culprits. DC power supply wires will induce noise also in the first few nodes due to the lack of filtering in the first couple of stages, (pulsating DC). That field coil you removed was probably part of your PS filter network. You did try extra 20uF Ecap though so that should have helped. Study the web for ideas. Geofex has some tube amp troubleshooting procedures. Stop by any time, I'll always try to help. So will many others. Good luck with your amp...Goose
Last Edited by Barley Nectar on Apr 05, 2015 7:55 PM
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Barley Nectar
744 posts
Apr 05, 2015
7:51 PM
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Bliz, if the hum is affected by the volume pot then the problem is before that part of the circuit. Loose jacks and pots will cause hum, (Bad Ground). Tighten those mounting nuts. If your amp uses a shorting type jack at the input, check it close to see if the little switch is making and make sure the jack is clean. Same with speaker jacks, clean! Hum is often caused by poor grounds and ground loops. Ground loops occure when something is grounded to the chassis in more than one place. Input jack and speaker jacks as well as pots are suspicious, as are crappy old solder joints. The Masco build uses isolating washers on all jacks. Every circuit ground goes to the ground buss which is tied to a PT bolt. The AC line ground wire ties to a different PT bolt and the filiment and HV secondary winding center taps tie to yet another PT bolt. This setup keeps signal and power currents from running thru the steel chassis. The way the old amps were built, it's a wonder any of them are quiet!...Goose
Last Edited by Barley Nectar on Apr 05, 2015 8:01 PM
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Barley Nectar
746 posts
Apr 06, 2015
10:16 AM
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Last of the pics for the Masco build.
DC bridge circuit for V1, 6SJ7
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Barley Nectar
747 posts
Apr 06, 2015
10:25 AM
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And the Craigslist mystery amp. It is Working but needs attention. Pretty nice shape for early 50's! I have no back panel for it. Does anyone have this color brown airplane cloth (covering)?
This one will sit on the sidelines for a while. My Gibson '56 GA-20 Two Tone is on deck!
Last Edited by Barley Nectar on Apr 06, 2015 10:29 AM
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Bilzharp
51 posts
Apr 06, 2015
1:19 PM
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I'd probably drive 200mi for a Flot-a-tone too! I recapped one of these for a buddy. Makes a great harp amp. Some pretty wacky circuits on the one I did though. Input jacks wired straight to the 1st stage control grid - not even a resistor! The pilot light was powered off the power tube cathode circuit and flickered when you played through amp!? Yours is a beauty!
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Barley Nectar
748 posts
Apr 06, 2015
4:33 PM
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The top chassis has been hacked. The bottom looks pretty original. Tone control is inop. Amp is bright but it sounded amazingly good with a Strat plugged in. Those old caps are not humming either! I'll probably just restore this, no mods. Bliz, do you have a schematic? I found one but don't know if it matches, have not checked. Rock on...Goose
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HawkeyeKane
2758 posts
Apr 07, 2015
10:13 AM
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That Flot looks like several 40's & 50's Silvertones I've seen. From what I can tell, Flots came from Milwaukee under LoDuca Bros. Ironically enough, I actually have some LoDuca Bros harmonicas my grandmother gave me for Christmas a while back.
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Hawkeye Kane - Hipbone Sam
Can I go home now...???
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Bilzharp
53 posts
Apr 09, 2015
12:50 PM
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Barley, I had to draw up my own schematic - which I can't seem to find right now. I'm sure I made a copy for my friend to keep with the amp. I'll check with him this weekend. I seem to recall that one of the preamp tubes was a dual triode and the other was a pentode. When his amp arrived the tubes had been removed and the chassis wasn't marked for their location. A bit of a headache figuring it out.
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Barley Nectar
754 posts
Apr 09, 2015
1:16 PM
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I'll see what I can do on the sound sample.
Blizharp, from what I've read on the Web, the
Flot-A-Tones varied their circuits at random, similar to Gibson, so any info is usefull. Thanks...BN
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Mojokane
808 posts
Apr 10, 2015
3:16 PM
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eye candy....
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Why is it that we all just can't get along?<
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Barley Nectar
755 posts
Apr 11, 2015
4:34 AM
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vintage MASCO ME-18 mono 6L6 tube amp amplifier pa/guitar/harp
No affilation...BN
Last Edited by Barley Nectar on Apr 11, 2015 4:36 AM
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Barley Nectar
760 posts
Apr 13, 2015
10:17 PM
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I have been asked for a price to build another Masco amp. Just the Chassis, no cab. I would use all new components, including iron. What would be a fair price, seat of the pants? Thanks...BN
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rogonzab
695 posts
Apr 14, 2015
7:15 AM
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It depends on how much you spend on components and how much time do you need to build it.
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Sorry for any misspell, english is not my first language.
Last Edited by rogonzab on Apr 14, 2015 7:16 AM
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Harpaholic
684 posts
Apr 14, 2015
9:47 AM
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Estimate $800-$900 depending on quality of parts and your labor.
I had a Kendrick clone chassis that cost $850 to build from scratch three years ago.
Mega tone amps charges $699 to completely gut your Masco
except transformers and rebuild to their specs.
Get at least 50% up front!
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Barley Nectar
762 posts
Apr 14, 2015
11:06 AM
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I was thinking less but have to do a price workup. I gave the guy a guesstimate of $600. Not a final price by any means. He is already squirming. It's no wonder builders go under so quickly. Not an easy business...BN
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Mojokane
816 posts
Apr 14, 2015
8:23 PM
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Except transformers...coool.
I wonder what they would sound like after Mega Tone is done with em...
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Yes, there are blues in Hawaii.
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