Soundcraftsmen A5002 X2...

[Loud & Clear]

:yes:Thank you Jailtime. Yes, Soundcraftsmen gear is certainly a handful. Especially when your trying to pull a stunt like I am here... :scratch2: Funny, all that power just to listen at around a 3 to 6 watt RMS level. It's the headroom I need. The program material I listen to has a lot of subsonics. I was listening to some Queensryche music the other day using my S.C. A2502 amplifier. I had to reassure myself I was still on the right track. Sure enough, and true to form, I was listening at a comfortable 3 watts per side, and every so often (in the blink of an Eye) I would see the truclip L.E.D.'s light up. Just a quick flash of a few milliseconds, but it happened often. So I knew I was still on the right track. :thmbsp: 3 watts to 250 watts faster than greased lightning... :yes:

 

[BobbyBluz]

We sold Soundcraftsmen along with BGW in the 80's. We went through several different amps in our service workshop system, a couple of Soundcraftsmen plus a BGW 750B in the rack were the in usual configuration. We had a pair of large wall-mounted Tannoy monitors to listen to the amps of our choice through. I still have an AE2420 with the correct original calibrated mic for it plus a couple of other stereo EQ's in storage.

 

[Loud & Clear]

We sold Soundcraftsmen along with BGW in the 80's. We went through several different amps in our service workshop system, a couple of Soundcraftsmen plus a BGW 750B in the rack were the in usual configuration. We had a pair of large wall-mounted Tannoy monitors to listen to the amps of our choice through. I still have an AE2420 with the correct original calibrated mic for it plus a couple of other stereo EQ's in storage.

 

[Loud & Clear]

Sorry for the delay. As I said at the start of this thread, I will post pictures and update when I can get a chance to work on these amplifiers. So, lets see, we have all the tak-man 1/2w REY resistors installed, and the ohmite "non inductive" 5w resistor on the outputs. I have also changed out all the lytics, and the film units with superior units. So I guess these are pretty much finish accept for triple checking the boards, the foil side also needs a good cleaning to remove the rosin, I do not want any reaction between passive components. Then I will test them, and report back. I have not finished the capacitor banks yet, but I will get to that. I'm also rebuilding a S.C. AE2000 eq. analyzer (I will post a new thread on that build soon) that is a real challenge. Guess maybe I shouldn't be working on 3 soundcraftsmen units at once. But I cannot resist the challenge. Thank you for your interest in my work.

 

[goat67]

Did you replace the Bias Pots?

 

[Loud & Clear]

Did you replace the Bias Pots?

Actually I haven't. But thank you for reminding me. I was going to remove those, deoxidize them, and then test them. I would rather use the originals in this case, as the replacement pots these days are (as with most things) not the quality they used to be. That being said, if they need replacement, I believe I would opt for the Bourne units for replacement. Thanks again goat67.

 

[Loud & Clear]

Emitter resistor for the Soundcraftsmen A5002s. These are Ohmite low inductance 1% wirewound units. I'll take a picture or two when I get them installed. Often times I forget to take play by play pictures of my work, as it isn't high on my priority list when I am trying to concentrate on my work. But I will do my best...

 

[Loud & Clear]

goat67 technically, if you want performance that does not drift, and is much more reliable when it comes to that 100ohm bias pot. Assuming the tinkering is complete, and the bias is adjusted where it should be, you simply measure resistance from the wiper (center pin) of the carbon film potentiometer to the 270ohm (330ohm in some cases) side of the open end of the pot. When you find that measurement and are sure it is correct. Remove the potentiometer and install a .5 or 1% high quality metal film resistor of the value you measured. In some cases you may have to install two (2) resistors either in a series or parallel situation to get you bias resistor value, even if you are reasonably close. I've seen several amps biased in this fashion. BGW comes to mind right off. Works great and it doesn't matter if it were to get bumped etc...

 

[Loud & Clear]

After replacing the emitter resistors (pictures below) I think it would be only right for me to explain to the S.Q. crowd, that it is of the utmost importance that you remove these driver boards and at least inspect "every" solder joint. There was not one board that did not have at least two cracked solder joints (do to age) on them, especially around the headers. On one of the boards, pretty much every solder joint on the headers had a nice crack around it. That is a problem that will most certainly reveal itself sooner or later. As a matter of fact, I never did even listen to these amplifiers before I started building them. So "in fact" there may have been pre existing conditions that I never got a chance to hear. Anyway I hope my posts are of at least some help to you Soundcraftsmen bretheren. Thank you for looking, and stay tuned. I will finish these one day.

 

[geode]

Nice work Keep it coming.

 

[Loud & Clear]

Here are a few blurry pictures. I have had a chance to work on this project a little more. I have 2 circuit gold plated molex headers coming for the ins/outs on the amplifier boards. Thanks...

 

[Loud & Clear]

I am an extremely busy person. But here are a couple pictures I thought I would post. Note: The above amplifier boards and new .25ohm low inductance emitters resistors couldn't work, or sound better. I'm still plugging away at the capacitor banks.I will go into more detail on all of this, when I get a few minutes. Thanks

 

[Loud & Clear]

Well, I gave into temptation. I have started disassembling my amplifiers. I have begun to add emitter resistors and transistor sockets. Therefore adding 4 extra output transistors per amplifier 2 per channel... I know 4 per board is better than 3, makes em' more rugged indeed...

Center xsister socket and emitter resistor were added. See below...

 

[Loud & Clear]

Finally back at this again. Generally, it is the wait for parts the is taking the most time...

I found I could not do the dual mono conversion. Well, I could, but would have to eliminate the protect circuitry. So I am going just going to make them high performance stereo amplifiers. The pictures show a look at the capacitor banks and the bridge rectifier setup. The .1uf film caps in parallel with all four diodes in each rectifier will slow the diode switching down to help prevent any P.S. oscillations caused by high speed diode switching. Thanks...

 

[Loud & Clear]

I actually have one of these amplifiers done. I didn't want to post pictures till I have them both done. The sound and dynamic range are out of this world. Never heard anything like it. More about that later.

Right now I have a question for Soundcraftsmen H class owners. Goat67, you out there??? Was wondering if the Variable/Auto Buffer L.E.D.'s are supposed to be instant on and instant off? I believe (via my blue led choice) I have inadvertently changed the way that lighting circuit works. I get a relatively fast attack, and very slow decay. My guess is they are supposed to be instantaneous. I have an idea on the cause, but first I need to know what is inherent of the units?

Thanks, Tom

 

[goat67]

I actually have one of these amplifiers done. I didn't want to post pictures till I have them both done. The sound and dynamic range are out of this world. Never heard anything like it. More about that later.

Right now I have a question for Soundcraftsmen H class owners. Goat67, you out there??? Was wondering if the Variable/Auto Buffer L.E.D.'s are supposed to be instant on and instant off? I believe (via my blue led choice) I have inadvertently changed the way that lighting circuit works. I get a relatively fast attack, and very slow decay. My guess is they are supposed to be instantaneous. I have an idea on the cause, but first I need to know what is inherent of the units?

Thanks, Tom

I am not sure what you are asking. The LEDS should respond to the output and should not have a slow decay.

 

[Loud & Clear]

Wow, kudos to you. Love the Soundcraftsmen gear especially A5001 and the one with the big VU meters. Was onto the bay and saw a vintage Soundcraftsmen receiver. Didn't even know they made receivers. Learn something new each day..
Kudos and good luck with all you've done.. wow..

Thank you very much MarZutra.

I am not sure what you are asking. The LEDS should respond to the output and should not have a slow decay.

Ok, Thanks. I'm getting a fast attack slow decay on rail switching indicators. I can see I have to make a few changes. Very hard these days to find "standard" l.e.d.'s everything is way to bright now a days. Not every application takes an l.e.d. with 7000mcd output. I dumbed down some super bright l.e.d.'s for that circuit, so I could get the color I wanted. Seems the characteristics of my "dumbed down" circuit is not going to work. I had to be sure how those indicators are supposed to function. An l.e.d. is a diode after all. Many Thanks...

 

[Loud & Clear]

Here are a few pictures of one amplifier being put through it's paces. These are just a few quick snapshot taken quickly. I've yet to illuminate the clip indicators. The amplifier is just to powerful and I worry about the speaker, even though the are made to handle the "theoretical" power from this amp. The only way I can come up with to describe this amp, is 12 watts sound like 200 watts would from the normal A5002 and "extremely" dynamic/clean. Very happy with my design so far. I have to fix a glitch in the rail switching indicator lighting. That is not a big deal, but time consuming. This amplifier crackled into life without incident, it just (to my surprise) worked right off. I will post a complete rundown on both amplifiers when I have them done. Thanks.

 

[just dave]

Oh man that setup is gonna sound awesome!!!! Congrats.

 

[Loud & Clear]

Oh man that setup is gonna sound awesome!!!! Congrats.

Thank you just dave. I'm spread pretty thin, but I am exited to get it accomplished and give it a listen. "Thoughts Become Things"...