Anything you can afford will be that old.
#Sks 2n3055 how to
And the board are glued in, I haven't even figured out how to get the boards out to work on them. I bought one last year and it lasted two sessions before the electrolytic caps (probably) froze the sweep. They still sell actual analog panel meters. If you can't buy a scope and probes or VOM, buy a 50 microamp meter and make a 2 VAC meter. Your problem may be your boards are laid out for slow parts, and they don't make those anymore, anywhere. They are patently something faster, the factory that made those old slow parts in Indianapolis has been demolished and replaced by a shopping mall, I believe. You may be able to use the "2n3055" you have, if it is oscillating and you get rid of it. You need to use a scope or do the VOM check I detailed above to check for oscillation. If you don't do a Vceo check on your parts and an soa check, you have no idea if they are real or not if not buying from an authorized distributor Both have European warehouses, if you sign on you will be asked for your country. Dynaco had you wind them around the output caps, rather quaint.į sells real ON semi parts here in the US. You can make the inductor by winding any old thin wire around a china marker or fat grade school pencil.
#Sks 2n3055 mod
This mod is probably a good idea for any original old PWB designed to drive 2n3055 or earlier that wasn't tested for parts faster than that. See the "TIP mod" for the dynaco ST120 on greg dunn's website. Put the little caps in on the drivers, and if you don't have a zobel network on the output (12 turn inductor in series transistor collector junction to speaker hot, 1 k resistor and a cap in series between speaker hot and speaker ground) add one. They also have a higher Vceo which is important in my ST120, and they have a specified safe operating area, which hadn't been defined in 1966 IMHO. Personally I like the MJ15015G as a sub for the 2n3055, they are about $3 cheaper than MJ15003 and about $2.50 cheaper than MJ21194G. This test won't work with DVM's, they just produce random numbers when subjected to RF oscillations. Still have significant AC voltage on the output, for sure it is RF. Then change the cap to 470 pf or something. Any significant voltage you can't hear, could be RF oscillation.
47 uf (microfarad in newspeak) capacitor in series with the input on VAC and measure the output with the input shorted. To detect oscillation without a scope, if you have an old fashioned VOM with a 2VAC and 20 VAC scales, put a.
It did have a low volume distortion, that is another issue. Not nearly as vile as the reviews in 1966 said it was. I've never heard my ST120 with the original 2n3772 or RCA 5 digit (high Vceo 2n3055), those were burnt up when I bought it, but with NTE60 (probably MJ15003 equivalents) it always sounded okay at decent volume. Faster output transistors should give better sound according to the simulations done by someone on the Leak Delta 70, but oscillations sound bad and consume the transistor doing the wrong thing.
#Sks 2n3055 driver
On dynaco ST120 amps, we put ~22 pf between base and emitter of the driver transistors ahead of the output transistors. You can't buy real 2n3055, everything is faster.
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