I'm looking for the circuit and ETI article for the mini-amp ETI453 from ETI April 1980 (also published (I think) as the HE105.) I've got a couple of PCBs but have long ago thrown out the ETI mag. It seems to use an op-amp, three small-signal transistors and two power transistors, from the pcb pattern. Any old-timers out there who can help shed any light?
What I did after some helpful info from Phil (and some abuse) about which issue, was to join the big library in sydney (they keep copies ) and copy article.
"yaputya"
** Is the PCB designed to accept PSU components and two TO3 devices on heatsinks like this:... Phil
I would still have it around here somewhere
I got old "Audio Projects from ETI" mag with this amp, it uses LM301, BC557, BC639/BC640 and TIP31/32 for output stage. If you provide working email I can scan and send you the article.
Tom
** That is the same PCB I used a few times back in the early 80s - but modified it so TO3s (ie 2N3055 and MJ2955 ) would fit in place of the TO220s.
Configured it as a Wien bridge, self oscillating, sine wave power amplifier using a 6.3 volt bulb for amplitude stability. The output drove a 15 watt valve output transformer ( A&R ) in reverse to produce a 240V, 50 Hz sine wave with adjustable frequency over a narrow range.
The purpose was fine pitch tuning for a synchronous turntable.
Was published in the design ideas pages of ETI in the early 80s.
.... Phil
heatsinks like this:
No, it doesn't seem to have rectifiers etc. and has 6 pads near the edge of the pcb that would take 2 TO220 transistors, not TO3s. PCB is 83mm x 50mm, coded ETI453.
BC639/BC640 and TIP31/32 for output stage. If you
Thanks, I use a working email for ngs so just reply to sender.
BC639/BC640 and TIP31/32 for output stage.
modified it so TO3s (ie 2N3055 and MJ2955 ) would fit in
using a 6.3 volt bulb for amplitude stability. The
a 240V, 50 Hz sine wave with adjustable frequency
That is interesting, could you scan your circuit and post it somewhere (or just email it to me).
"yaputya"
** After 30 years, I no longer have a copy.Silicon Chip magazine have back issues of most EA and ETI mags and will copy articles for a small fee.
... Phil
Hi yaputya I built the ERI453 way back when and found it again half an hour ago when cleaning out my workshop. (I found your request when Googling it myself) If you're still looking for the article I'm sure I have it.
If so, email me at snipped-for-privacy@yahoo.com (Please put the word 'orchid' in the subject to avoid the spam filter.)
Barry
cleaning out my workshop. (I found your request when
the subject to avoid the spam filter.)
Thanks very much for the offer, but I've already got the ETI article from someone else on aus.electronics!
cleaning out my workshop. (I found your request when
in the subject to avoid the spam filter.)
someone else on aus.electronics!
Have you built the amp yet ?
from
cleaning out my workshop. (I found your request when
in the subject to avoid the spam filter.)
someone else on aus.electronics!
I actually built two of them about 30 years ago to replace the power amps in a stereo gramophone unit. Last year I removed them before the old unit was chucked out, they are now used to boost the speaker audio from my workshop PC. They work well enough for the job, but probably would sound even better if the op-amps were replaced with NE5534s.
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