I was going to wait till I cleaned up the two ugly dropping resistors in the bias circuit before posting pics, but it'll be awhile before I have a $130 to send to Mouser for the right value and a bunch of other stuff I need. Simply incredible how .50¢ here $2.00 there adds up to $130 for a handful of little parts. What's the world coming to? I gotta stop this amp thing, when does the DIY jones wear off?
http://picasaweb.google.com/10412328569 ... directlink
So, dead silent except for the nice tube rush, the ptp keeps working well for me. Bright, immediate, and snappy and I really think the ptp is part of this. I started out intending to use a board and lined the tubes up straight across the back, then didn't feel like making the board. So the terminal strips wound up laid out like a board with ptp off of them. It really would have been better to do it true ptp with the tubes laid out like a Matchless with V1 near the pots and V2 btwn V1 and the output tubes, that way I could have avoided the one shielded run from front to back. But it's silent and works great so I'm satisfied. The OT secondary is a little ugly sticking up as it is but it's a reused tranny with short leads and it's also a good way to keep it away from the low level wires.
The PT is the TDS/West unit as I need euro taps, and if the Harvard was dud I'd have a PT I wanted. Bias is off the HT Marshall style, I needed 330K as the dropping resistor to get the right range. Plates are 330V, bias -24, 25mA current. I was hoping to hit ~300V like the schematic but I guess the TDS at 285V was a touch too high. I will try the tubes at 35mA which will drop the plate V but wanted to try it cooler first as I believe Fender would have shipped this at less than 70%. The rest of the voltages are practically spot on to the schematic. BTW my 2nd TDS PT - very very cool running. Very nice.
Sounds divine - really. Absolutely great tweed Fender copy. I only used modern parts in the power string and the bias, tubes and all the coupling capacitors and resistors are 40-60 years old stuff I had stashed, and it's rock solid. Caps were all in close spec and apparently not leaking
The speaker is an old Canadian EMC from the 60s I had saved up for 20 years waiting for something special. All I'm missing is an old domino mica cap at 500pf. Anyone???People here were curious about the Tungstan 10 (Weber 10A125-O?). I kept high hopes but was suspicious of the smooth undoped cone, and I thought it was a dud here - glad I got it used. It's warm, sweet, twangy at lower volumes but breaks up much too quickly and the distortion is fuzzy/buzzy and monolithic, ie the breakup sounds the same from 4-10 - just gets louder. It doesn't have that nice point of getting it's hair up before it distorts, it just distorts. The old Canadian EMC Jensen (C10Q?) sounds every bit as sweet but breaks up more progressively and sounds just perfect and vintage here. I think I just prefer the snap of ceramics too. I'm scared to blow it, but the sweet spot on this amp is around 10-11 o'clock just when it starts to get some bite and hair on it and you can make it go from clean and sweet to hard and biting just with pick attack. I got a 5E3 if I want to make a big racket. Since the old lady next door yelled at me waving a butter knife I haven't had a chance to test the head flat out through a bigger cab with a G12H30 Anni, but I tried it quickly at a medium volume and can already hear that it'll crank like a tweed fixed bias fender.
The Harvard doesn't sound anything like a 5E3, it sounds like a little version of my 5F6A. If memory serves it sounds like a Brown Deluxe/Princeton. It's been a while since I played a small fixed bias amp - it's great. For those people who think the 5E3 is too dirty and out of control this may be just the tight twangy little amp for you. Might be better to just build a Harvard than go chasing your tail modding a 5E3.
I love the 3 inputs, they actually work and are useful, very Goldilocks. The Low really cleans it up and makes it mellow twangy and bouncy, the High burns red hot, the Med is in btwn - nice. When trouble-shooting the bad jack, I tried clipping a 1 meg load resistor in place. I didn't spend too much time on it but it tamed it a touch. It's wilder without. I'd definitely keep the 3 inputs as is and I think you'll lose something unique if you go the standard 68K/68K-1M arrangement.
I tried David Root's suggestion of using a 6BF6 to clean it up (how can you not love a $3 NOS tube?) it works, but I can clean up just as well using the low input or the volume on the guitar. Also, 6AV6 is the way to go IMO but I haven't tried HBs yet. I started out with the 6AT6 and it was great, but it just pranced over the fence and ran off with the 6AV6. I found a web pict of a real 5F10 w/ the cab label showing 6AV6 printed (not over-written) so, near the end of the 5F10 some Bakersfield cowboy test-driver must have told Leo he liked it better hotter and they changed it. Wonder if Cropper had a 6AV6?
There's a good clip on YouTube of a vintage Harvard, that one is a little warmer, fuller, and deeper, mine's more tight and middy. I think the thinner bigger baffle on the original might be a part of that. The Marshall carcass has a very tight 1/2" thick baffle.
The amp sings with my G&L, twangy snarly heaven. I hit it out of the park with this one. The Victoria equivalent is $2000. And, they're not using cool old caps or tubes or speaker. The broken Marshall cost me $50, the TDS PT $120, add probably $150 in parts I was out of and a couple 7 pins from ebay, the rest I had. I feel proudly resourceful.
BTW face plate is just plexi over good gold art paper run through my printer with the best I could figure out using Word.
If I can find some friends with studio access or a place to make noise with some decent recording gear I'll try and do some clips.
If anyone sees anything not right please point out.
Thanks for all the help everyone.
