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#1
Well, I've been eying harmony amps on Ebay for a while. After bidding on more than twenty (no joke!), I wound up with this sucker





And check out the condition of the schematic! I havn't seen to many in this good of shape! Original knobs and all al well.



And now the bad news. Has some major hum issues, probably because of a bad multisection capacitor. And worst yet, the speaker is torn! Noooooo!



I'm gonna re cap it, install a grounded power cord, and either replace (ouch) or repair the speaker.


I will need help in all likelihood, I've modded an Epi VJ and built a dozen or so pedals, but have never done anything with vintage amps. I'm not to worried about "Vintage condition", the amp ain't worth much anyway. If something needs to be done to make it sound better, I'll do it.

Never done any speaker repair, I don't know how bad the damage is or if it will be an easy or possible fix.

The cab is not that great as far as structure goes, but it looks cool and I'd rather not rehouse the amp.
#3
The cabs are allegedly particle board, so I was worried some reinforcement would be necessary.

As far as the speaker goes, I have a 1964 Oxford AINiCo 12" I was thinking about putting in there. I know the speaker in there is an 8", but if you look at the top pic, there seems to be a lot of room. Its a bummer though, since the speaker in there IS and awesome old Jenson...
#4
I would definitely add more filtering and replace that old dried up original filter cap.

Lots of room in the chassis...I would add another gain stage or maybe some tube tremolo.
#6
Link to the schematic:
http://schematicheaven.com/bargainbin/harmony_400a.pdf

I was thinking about another gain stage, But this amp has some really nice cleans and slight overdrive, and I'm not hurting for amps with major gain on tap. The tube tremolo sounds pretty cool though.

Were would a logical place be to add more filtering?

Jim and Chris are the first posters, well, I sure won't be lacking knowledgeable help!
#7
Haha, only 67$, and I got it on Ebay!
They usually go for 100$ to 200$.
#9
But you're not to bad about vintage gear, and have more common sense than 99.9% of those on UG.

Edit: And sorry about the double post.
#10
You could add another gain stage for a make up stage, then you could add a tone stack. You could always add a little switch of push pull pot to bypass the stage.

The tube tremolo is super easy to implement, only about 10 components an a dual triode.

You add the filtering in the power section to filter out AC ripple.

Whats your B+, looking at the schem it seems it would be low?
#11
Actually, the amp isn't hear yet, hopefully it will be tomorrow.

And I'm afraid you have overestimated my electronics abilities.
No idea where in the power section, or what exactly I would add, (Cap?) or really much at all.
I can read a schem (mostly), discharge caps/safety stuff, bias an amp, maybe ad a basic tonestack, but for something like an additional gain stage, decent tonestack and tube trem, I will need the kind of instructions one gives a two year old.
#14
Yeah, I'll definitely play it first.
Depending on the speak, I'll take care of that, and install a 3-prong power cord.
Then I'll take care of the filter cap. Would it be a good idea to replace other caps in there as well at this point?
Edit: The seller promised working condition, albeit noisy working condition. Fairly big sell, I'm not to worried.
#16
Cool, that's what I was thinking as well. Won't be to hard considering the amount of electro's in this amp.
#18
Were those made by Silvertone? The cabinet and grill cloth look just like my Silvertones. If it's same stuff, it's pretty much cardboard. I have yet to find an amp made out of that stuff that doesn't rattle when cranked. Looks like a cool project though.
#19
Made in Chicago, same factory as the Silvertone's I have heard, not sure though.
#20
Major Update: The amp is here! Sounds great so far, but the speaker will probably have to go. Totally ripped all the way through, got nasty, farty distortion when playing multiple notes at once if the amp is really being pushed.
Structurally, the amp is great. Far better condition than the pics led me to expect, very sturdy as well.
The hum is there and it is annoying, but not horrible. Only noticeable when you're not playing. Pics coming soon. I'll replace the power cable first, get some gut shots.
#21
EDIT: Pics resized.

Here come the pics, the lifeblood of UG. Solid construction:





Gut shot:





I have taken the amp apart, (after playing it for a half hour of course) and I realize that I have a couple of options.

The speaker is ripped pretty bad, I either need to repair or replace it. It is a 1958 Jensen, I verified. Stamped onto the speaker bell is the following:
SP832-HAR
220843

The bottom line show the manufacturer and date, and HAR= Harmony, but I don't know what the other numbers are. Anyway, PICS!







At this point, I think I will replace the speaker, at least temporarily. Here is the speaker baffle:





To small for a 12", and if I put a 10" in I would have to recut the hole. I have a crappy 8" behringer from an old practice amp, but I think I'll just wire this here:





To a 1/4" jack, then I can use the onboard speaker or run a line out for maximum versatility.
Last edited by SVStee at Dec 15, 2008,
#22
Alright, first mod implemented. I have replaced the line to the speaker with a 1/4" jack, like so:





Ran into a problem, maybe. I only had a little time to try it, but I don't think it was working into my 1x12 cab. the amp takes some time to power up though, so maybe I just didn't wait long enough. On the other hand, I don't want the amp running with no place for the juice to go. What do I do?
#23
Are you trying to run the original speaker and external speaker?

Is the + going to tip and - to sleeve.

Yes if no standby switch then the amp will take a min or so to power up. Filaments need to heat up.

If you have no load connected you could destroy the OT. They are expensive (usually) and a replacement will be hard to find with your amp.
#24
No, I'm going to run either/or, as in run the amp into a 4x12" or use a short cable to run it to the speaker mounted in the amp.
No standby switch, and no power indicator either. How would I ad an L.E.D. as a power indicator?
#25
Alright, got the speaker out thing all taken care of, works great.

Next in line is dealing with the 2-prong power cord. My dad got me one of these
http://www.alliedelec.com/Search/ProductDetail.aspx?SKU=627-4000&MPN=HBL5266C&R=627-4000&SEARCH=627-4000&DESC=HBL5266C?utm_source=Allied&utm_medium=merchandising&utm_campaign=Allied_Top_Sellers&utm_content=627-4000

for free from his work, I think I'll use it, I know how to set them up. My question is, which is positive and negative in this schematic, the one that goes to the off/on switch or the one that goes to V3 and R10?
http://schematicheaven.com/bargainbin/harmony_400a.pdf

Thanks for all the help!

EDIT: Does it matter? As long as I get the grounding right can either the left or right prong go to the switch?
Last edited by SVStee at Dec 16, 2008,
#26
OK, sorry for posting so much but I had the day off and plenty of time to work on the amp. Played it for a good while today and noticed some things. That farty, bad distortion I described at the beginning of the thread wasn't entirely the ripped speaker, the amp sounds that way when pushed. Anywhere over halfway up and it also starts to compress like no other. Doesn't take pedals to well, either. My DIY SHO, LBP, and other assorted overdrive/booster seemed to do nothing but amplify the negative qualities of this amp.
So I have some questions:
1: Could the farty distortion sound and major compression be a result of damage I did to the OT? I had it on for a minute or so with a miswired jack, giving the juice no where to go.
2: Could the farty distortion sound and major compression be a result of bad/old tubes? The tubes aren't microphonic, but could they still cause my problems? I can get replacements on the 'bay for fairly cheap.
3: As long as I get the grounding right can either the left or right prong of the power cord go to the amp's off/on switch?
#28
Which prong would be live?
And what exactly would the symptoms of a damaged output transformer be?
EDIT: would it be worth it replace the rectifier tube as well, or just pre and power?
#29
Live should have a L beside it on the IEC socket. Otherwise it would be the black wire if you have no socket and just strain relief.

Take a push-pull amp and remove one output tube. Turn your amp on and play, hear that terrible sound, that's what a shot OT sounds like.

Yes I would definitely replace the recto. There is no vintage mojo or mystique in the amp. I would replace whatever needs replacing. What kind of tubes are they btw?
#30
35W4 power
12AU6 pre
50C5 recto
All original Harmony tubes.

And the amp sounds nice between 1/4 and 1/2 up, but if I give it more juice, yucky. Probably tubes.

I'll replace the cable, check the amp, then re-cap. Then wait for tubes to show up.

What would happen if I wired the power cord wrong?
#33
Quick question, the instructions for installing the grounded power cord says to "Attach the green wire(ground) to the nearest transformer bolt you can find." But this amp has no transformer bolts. would I attach it to the base of a transformer (If so, which one? Does it matter?) or just anywhere on the chassis?
#34
Just attach it to the same place as the rest of the grounds on the amp if you can. Failing that nearest chassis/ground point.
#35
^actually no. You want the line in voltage to have it's on ground.

You don't wanna attach it with your pre, screen, etc grounds.


Use terminal rings for the best connection.
#37
Ground loops and ground interference I believe. Grounds don't all have the same potential, you don't want them all just jumbling together.

I don't know a whole lot about that aspect technically. I do know however that you always have a separate line in ground, always see it done like that.
#38
So where do I put it then? I wasn't planning on putting it with the other grounds, but just attaching it to the chassis is good enough, right?
#39
Quote by SVStee
35W4 power
12AU6 pre
50C5 recto
All original Harmony tubes.

And the amp sounds nice between 1/4 and 1/2 up, but if I give it more juice, yucky. Probably tubes.

I'll replace the cable, check the amp, then re-cap. Then wait for tubes to show up.

What would happen if I wired the power cord wrong?

might want to give that a higher gain tube.
Current Gear:
LTD MH-400 with Gotoh GE1996T (EMG 85/60)
PRS SE Custom 24 (Suhr SSH+/SSV)
Ibanez RG3120 Prestige (Dimarzio Titans)
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Audient iD22 interface
Peavey Revalver 4, UAD Friedman BE100/DS40
Adam S3A monitors
Quote by Anonden
You CAN play anything with anything....but some guitars sound right for some things, and not for others. Single coils sound retarded for metal, though those who are apeshit about harpsichord probably beg to differ.
#40
Quote by SVStee
So where do I put it then? I wasn't planning on putting it with the other grounds, but just attaching it to the chassis is good enough, right?

Just have a seperate ground for it.....bolt, terminal ring, lock washer.
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