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Valve or tube amps should not be operated upside down like the Fenders! The heat generated shortens the valve/tube life and cooks the components like resistors, capacitors etc! i e electrolytes start to leak and spill contents ! Fitting a quiet fan inside helps to dissipate the heat!

Well done!

Just stumbled upon your video. I was just gifted in 1962 A model of that scope from my dad’s trade school from his electronics lab class. It works when plugging it in. I just want to tear it apart and replace all the caps and put it back into original condition and use it on my bench. .

Outstanding

Quiet* moment

Very in depth video but could be considerably condensed. Hell of a lot of sidetracked waffling…

I have the exact same amp, but mine was completed in the 42nd week of 1968, and yours was the 50th week. My faceplate is the short-lived "blackline" model. I am going to leave mine as the AC568 circuit, but change out the resistor to ground on the bias balance pot, and add a bias trim pot in parallel with the resistor, so I can have output tube matching and overall bias level adjustment. These hybrid fixed/cathode biased amps were biased on the cool side from the factory. Mine is at around 42% idle PD.

OK i don't know why it keeps getting removed but i keep trying to post where i found the clamping ring.

Lots of practical advice here. Thank you!

Transformer mounting bolts do not make a safe, reliable ground point because invariably the nuts will loosen up a little from speaker vibration as the amp is played and from tge car/truck/plane ride from gig to gig (the transformer laminations may shift and compress a little over time, and I suspect that the bolts might actually stretch slightly). Modern electrical codes require a separate dedicated earth-ground for the green wire from the power cord; old Fenders typically do not have an empty hole for a new dedicated grounding bolt so you're best off to solder the ground wire right to the chassis (it needn't be grounded to the same point as the transformer center taps, and indeed it's often better, less noisy, to have it connected to the chassis at least a few inches away from the other grounds)

Nice to see, that you got this scope operating again. I got the same kind and use it now and then and just now. I got it about 1980 on an auction. It had a fault back then, in the main transformer. It got a separate winding to supply the filament of the CRT, and it have a voltage at about -2900 V. So there was some spark-overs in the transformer. I then mounted a small other transformer for this filament, and then it have worked since :). Well today I was using it, and I discovered that the light bulbs for scale illumination had finished. So I shall try to find replacements, and then I saw your video. The inscription on lamp is 6.5V .15A.

I am doing the same thing to an AC568 so these videos go hand in hand with what im doing

I just bought 2 of these, which have the faceplate changed to black and the covering to white and blonde, so they look great, now I need to make the insides as cool.....great video

Fat Jimmy clarity is king! What model Fat jimmy is it?

I just aquired one of these , getting ready to check it out

Fantastic series! You've really thoroughly documented this process. I just picked up an AB165 Bassman, so this was very valuable information. Thanks!

Hi, i have a 502a too, and during the shipping crt broke, can anyone tell me where i can find one? Thanks

Thanx a bunch for making these video's. As I said looking into acquiring the unit, now I know for the most part what they are capable of 👍

Interesting, as I am looking at 2 units from an auction, both rather "molested" as they seem to come from a US army. We will see if there is any life in them.

I'm wondering why you would want to change an ab165. Aren't these a desireable circuit? I have a bandmaster ab165 and it roars with a Gibson.

i friend i have same unit my battery died so i removed battery put new one in but i forgot to keep power on unit while replacing, so now i am getting Cal required logo what can i do? how can i remove that logo Saying Cal reqiured please let me know if possible thank .

Hi friend i have same unit my battery died so i removed battery put new one in but i forgot to keep power on unit while replacing, so now i am getting Cal required logo what can i do? how can i remove that logo Saying Cal reqiured please let me know if possible thank .

It's Fat Jimmy, not Jimmy Fat.

I don't understand the title says changing from an AC568 to AA864 and the unit is an AB165 circuit.

Sounds really clean and clear absolutely fantastic

Nice video! There was a 502 (not sure if it was a "A" or not) that was at a startup company I worked at in the late 80s. The founder/boss had got it along with some other "junky" stuff from his last employer I think. My recollection is it had some problem and maybe only 1 channel worked. It got put into a storage room and most likely ended up in a dumpster years later after I left. It had a light shield on the CRT bezel and I think there was even a rubber face visor so it must have been used someplace with a lot of ambient light and glare. I have never been totally clear on the usefulness or applications for the dual beam feature on these.

...eh....well....im in love, what a wonderful oscilloscope

Would you be willing to sell one of them? I had two of them, but lost all of my tools last year and have been rebuilding my lab. Would be interested in getting one, I already have a decent scope but I really like the analog aspect, and the built-in curve tracer. Thanks for your time.

Oh my, Paul Carlson would be proud! Let alone me. What a magnificent lab. And it's sooooo enormous. Envious of that Tascam deck. Any rackmount hifi equipment is my thing :) The bulbs in 1:37 are absolutely gorgeous. Do you use them as a dim bulb tester?

What, No microwave oven? Who do you think you are? Lol Nice workshop brother

Hamer guitars are GREAT! I have three: a 1994 Daytona, a 1995 T-51 and a Studio arch-top. The Daytona is the best Strat style guitar that I’ve ever played.

8 ohms speakers quality is superb

@ 17:21 : the ubiquitious NE 555 , probably for the flip-flop function .

Is it possible to do the same thing with an ab165 circuit and convert it to the aa864?

WOW! i have a drip edge bassman that is the same circuit with the ab165 tube chart sticker as well. It is in the shop right now for power cord and electrolytics, but you have me wanting this mod pretty bad! I always wanted a little more clean headroom out of this amp and your results sounded glorious! Thank you for this awesomely detailed video! Was the tweed mod to the bass side included in the package or was that an add on you picked?

What a nice and clean lab, well-organized and surely pleasant to work in, even if there's not too much space :) Gets my seal of approval!

"forgot co calibrate my counter" hahaha :D

These vintage Tektronix scopes are absolutely beautiful, both inside and out. Pity that they're so rare in the former Eastern bloc (Poland etc.). I once had a ZRK OS-102 that was almost surely a copy of one of the Tek scopes, and it was a very nicely built behemoth that I wish I didn't have to sell... it took too much space in my then crammed room/lab and I needed cash to go to a concert I really couldn't miss, I think.

Great detail keep up the good work

That’s great I have 100 W master volume party I wonder if I can do something similar?

You did miss the date in the catalogue, it was dated 6/74...I currently have the RCA WR-50B signal generator on my bench, servicing it...I believe its about the same vintage. Id like to see a service video on this device. ~Jack, VEG

I really enjoyed this series! I really like this generator and have toyed many times of buying one....but I am just about outa room due to the fact of my large collections...one of them being test equipment. :) Neat to see the explanation on the rotary encoder, kinda hoping you would have opened it up to look on the inside. ~Jack, VEG

Very nice setup! I have the Tek 520 plain (pre-A), its sick and need fixin, like you...bad eyeballs, was a great scope when working! Really like your microscope, very impressive! ~Jack, VEG

Great video! Just out of interest- is that a P2 or P11 phosphor in the CRT?

I have the exact same amp. It sat in a friends closet for 25 years. Ben Fargen (Fargen Amps Sacramento) went through it and it is an ass kicker today

I have had a few inquires to the custom pickup, and if it is was truly wound in reverse. I can say yes for sure it is. The reason I know this is because I also own a stock SH-16 to compare to. When placed in the breadboard test environment, and wired parallel or series only using one side vs a standard Seymour Duncan other pickup to create combinations, it is easy to detect if two chosen coils are out of phase or in phase. It is the stock SH-16 that was my motivation for ordering a RWRP pickup, so I could make the combinations in the video. What I have done for this guitar is of course not normal wiring, especially the center position with such high ohm value. I have another almost identical guitar I put together with a three way, and standard wiring. I find it fun to try new schemes, and push the envelope a bit. There are lots of sources on the internet showing standard wiring schemes, this is just something different to be creative.

Great vid! At what point did you discover and replace the two bad resistors and diodes? I don’t think you went over that part?

Would love to see a restoration, as well as getting the "good" one in as perfect working order as possible. Those are such cute little scopes, with the bonus curve tracer!

Unfortunately, this is the same type of station as cheapo $50 ones on Amazon with the blower in the handle. The only thing you can do with this is remove those resistors and capacitors as you did. Forget about IC chips on large motherboards with groundplanes

Magic blue smoke?... I've always referred to it as "Releasing the Grey Ghost" lol