when I was 18 I worked for a company that manufactured really nice decade boxes (resistance, capacitance and inductance) . I wish I got a few then. Although I probably wouldn't have them today anyway. Oh well. I'm over it.
Another Eico ST 70 thread
- Thread starter nj pheonix
- Start date
s-petersen
Scott
I picked up a really nice one at Cabin fever in April for $5 It helped immensely on working on feedback and step attenuation for an amp I am toying with.
It does R's, C's, R's in series with C's and R's in parallel with C's
Someone completely rebuilt it with modern precision parts.
It's an Eico 1140A
It does R's, C's, R's in series with C's and R's in parallel with C's
Someone completely rebuilt it with modern precision parts.
It's an Eico 1140A
No idea what cabin fever is. Sounds like a nice piece. The company was IET labs. They got a lot bigger than when I was there. Looks like they were successful and bought out other companies. I think when I was there, there were 4 employees counting the 2 principals. They had some great government contracts.
s-petersen
Scott
There are many video's on youtube of cabin feever,They have huge auctions,mostly Sterling,steam,and hit and miss engine related,but this year there was an estate auction of someone who was into High voltage(Tesla society?)I think.Lots of tubes,mostly transmitting,tube testers etc..
Thanks Scott. I'll have to look into it
s-petersen
Scott
I looked at the IET boxes,the combo box is nice!,but expensive!,someday maybe.
they only sold 4 products when I worked for them. Well that's not entirely true . They had an r box. a precision r box, a c box, and l box. A cap meter, and they came out with a bridge at the end. Two brothers, ( I think at the time one brother was in MA, working for a defense contractor on the eye weapons tracking helmet for the apache) a woman who worked for Gruman (before they closed) did assembly and answered the phone. I did assembly , trouble shooting, quality control. and packing. Based on what their site looks like they've done well in the last 30 years. I probably could've had a whole set or 2 for cost, heck he might've gave me the blems. Oh well. (I don't need them, but they are cool toys) Oh yeah we used to make special order shielded versions too.
I thought this was interesting
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=141036712734
A bit overpriced, though there's a set of EPI bookshelf speakers needing a refoam asking for over 86,000 dollars. Its Ebay?
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=141036712734
A bit overpriced, though there's a set of EPI bookshelf speakers needing a refoam asking for over 86,000 dollars. Its Ebay?
Its as done now as its going to get done until the efb board gets here. I figure When Jon finishes other amp he'll ship as one piece. That being said. Put it in main listening room. Put on my main speakers. Plenty of power (91db sensitivity) . What i'd say is kind of contradictory. There's something very right about this amp. Sound stage, clarity, Its quieter than I thought it would be. Ok now for the nitpick, I don't think it ever gets tonally neutral. Somethings sound excellent. I don't know if i'd say anything sounds bad on it. I find some stuff I want to tinker with tone controls (I think its not quite right). I recently picked up a tone generator and a scope. Maybe someone could talk me through possibly diagnosing my perceived tone issue. I thought someone from the eico forum might have blazed this trail already. Most like Jon just want to ditch the tone section altogether. Maybe i'll end up being a convert yet. Maybe i'm just stubborn. I believe I can find tonal neutrality and a livable (good , or better) tone control section. I did put a square wave though it . My generator really doesn't make a clean square wave. seems like top slope of square wave isn't quite horizontal . Bottom does look horizontal is this clean enough to work with?
I did try the centering thing from the ST 84 thread once already although I was getting acquainted with scope and tone generator (I might've done it wrong) . My intention is to revisit that exercise.
At this point I do want to thank Everyone who got me this far. Special shout outs to Mark Batt radio who first got me up through dim bulb test when I got it. Scott Peterson , for holding my hand through the meat of the resurrection. To Jon Yaeger for blazing the trail and letting me plagiarize. To Dave Gillespie for Knowledge and patience as I tripped over my soldering pencil , schematics and naivety . If I missed anyone i'm sorry, I do appreciate all the help I got along the way.
I did try the centering thing from the ST 84 thread once already although I was getting acquainted with scope and tone generator (I might've done it wrong) . My intention is to revisit that exercise.
At this point I do want to thank Everyone who got me this far. Special shout outs to Mark Batt radio who first got me up through dim bulb test when I got it. Scott Peterson , for holding my hand through the meat of the resurrection. To Jon Yaeger for blazing the trail and letting me plagiarize. To Dave Gillespie for Knowledge and patience as I tripped over my soldering pencil , schematics and naivety . If I missed anyone i'm sorry, I do appreciate all the help I got along the way.
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ferninando
Lunatic Member
have you installed the 'input bandwidth" limiter as per Van Alstien?
Fernando, I have to admit I'm at a loss. Short answer no. Long answer, I'll have to look it up. Link maybe? On phone now maybe a little time on computer later I can do research. Wife coming back from out of town later. Probably won't be able to really look into it until tomorrow. Thanks
Brief look on my phone only turned up links for a Dynaco ST 70 mod under that title. This is an Eico integrated. I don't think there's a connection here. Please correct me if I'm wrong.
s-petersen
Scott
I think ,as far as the scope goes,it should have a calibrator built in to verify square wave response, if it looks good there,try different settings on your sig gen,also set the scope to DC as opposed to AC,as there is a cap in line with the AC function.The most important scales on the sig gen are 1k and 10k as far as working with audio.If you keep in mind the distortion in the sig gen you should be able to still use it if you maintain the similarity between the input and output.The sig gen may just need a recap.
Another thing that caused me trouble was not using a common ground between units.
I actually created a nasty feedback loop through the grounds between my amp,my scope and my sig gen.
I connected my scope probe to the amp ground and connected the scope ground to the speaker positive,when the sig gen was connected with a 3 prong plug, the grounds were crossed and things went crazy
Another thing that caused me trouble was not using a common ground between units.
I actually created a nasty feedback loop through the grounds between my amp,my scope and my sig gen.
I connected my scope probe to the amp ground and connected the scope ground to the speaker positive,when the sig gen was connected with a 3 prong plug, the grounds were crossed and things went crazy
NJ -- What is the frequency of the square wave display you posted -- and what exactly was it going through? The tone section and power amp section? Just the power amp? Just the tone section? It's hard to make an evaluation without knowing exactly what the display represents.
Dave
Dave
ferninando
Lunatic Member
my mistake. not dynaco st70, but eico st70.
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Dave that was just generator to scope to generator direct. I was trying show downward slope of upper horizontal section of signal. I'll and capture some signals at different points and different frequencies with a list to correspond with what you're seeing . Scott I appreciate the pointers on the scope. I am in fact an uber noob in scopography (yes I know that's not a word). Thanks for the thought anyway Ed
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Depending on the scope and frequency you are using, the slope is likely due to response issues in the scope. When you view square waves, because of the extreme response required for proper display, make sure your scope is set for a DC input setting. With an AC setting, the signal is supplied through an internal coupling cap to filter out the DC, but based on the frequency, such caps can also produce a less than perfect display due to the phase shift they create.
Also, make sure your camera is shooting dead on at the screen to eliminate any parallax error in your pics.
Dave
Also, make sure your camera is shooting dead on at the screen to eliminate any parallax error in your pics.
Dave
Thanks for the pointers. I had limited scope experience about 30 years ago. For all intents and purposes, I'm in the crawling stage. I discovered the sync between scope and generator. Trying to make waveform stand still was driving me crazy. I never would've thought to measure an AC signal on a DC setting. For sake of making this as simple as possible, what voltage should my input be (.5?).what frequencies should I be testing at?. Are there certain telling points along the signal path that I should be concentrating on. Also assuming (a large assumption) that the waveforms are clean but the gain at different frequencies wasn't linear( my perception of the not quite right tone balance) maybe it will point me to my issue (solution). Hopefully tomorrow I can spend some time with it. Thanks again for the help and the education. I did this on my phone if it doesn't make sense, it probably doesn't.
s-petersen
Scott
The first thing I would do is test the scope with the internal callibrator,to see if the scope or the sig gen is the problem with the slope.
The place to test would depend on weather you are just trying to flatten the tone controls,or the entire amplifier
The place to test would depend on weather you are just trying to flatten the tone controls,or the entire amplifier
I don't know why I found that funny Scott. In my mind I was hoping amp was flat and i'd be tweaking Tone section. Maybe my beliefs (hopes) are flawed. More than likely. I'm hoping amp is reasonably flat within its design limits. If that's not the case, I'd address that first. Otherwise the rest of the operation is pointless. I guess that would be my starting point. It wont happen today in any event. Maybe I can check scope today.
