Arfa Daily wrote:

Any of you good ol' boys across the pond, familiar with a Delco 15CFMT3 (or
might be a 25CFMT3 as it has two stickers on it, one red, one black, each
purporting to be the "service model number" ).

It's from a vintage Chevy, I believe, and a colleague asked me to have a
quick look, and that's all it's gonna be, as I really don't have the time.
Initially, it had instability at about 50Hz, dependant on vol control
setting, It has a multi-section can-type cap in the back right corner, and
this seems to be open circuit on one of its sections. I hung a 1000uF
temporarily across the bad section, and that knocked the instability problem
on the head. I then tried the radio. There is plenty of livliness on AM, as
in it picks up a few stations, and there are lots of shortwave-like birdies,
but that is without a proper antenna connected, and in an electrically
pretty noisy environment (my shop!). On FM, it seems a bit insensitive, but
again, that might be down to a poorly matched rod antenna that I am hanging
on it. I don't know how well these old fellas performed in the first place.
If they were anything like British ones from the same era, then it's not
very well as I remember.

So, on to the 8 track bit of it. Mechanically, it all works, including track
selection, but audio-wise, there is just a horrendous mess on both channels.
There may be audio at the back of it all, but nothing recognisable. It's
hard to describe the noise. Sort of a very random, but continuous, distorted
'crackle'. Both channels exactly the same, and controlled by the volume
control. Given that the radio section / output stage works (sorta !) I am
guessing that this other problem must be in the 8 track head amp somewhere.
I really am not going to go looking for it, as I really don't have the time
or the inclination. I am not looking for general repair advice on it, as I
repair hifi equipment for a living as most of you know, so am well familiar
with fault finding. All I am looking for is if anyone remembers the model
and can say " Oh yes, That was a really common problem. It's C29 " or
whatever.

So, anyone got anything for me ? TIA

Arfa

15CFMT3 = Sams AR-114
25CFMT3 = not listed.


I have a copy of Sams AR-114, if you need any information from it.
I'll try to dig it out for you. The biggest failure in most of the
various models was noisy or dead transistors, or motor noise from the
motor's speed control circuit, caused by poor grounds or bad
capacitors. A failing motor would arc, and radiate noise into the
preamp, as well. A scope made short work of that problem. I worked on
hundreds of those Delco 8 track tape decks in the '70s.


AR-114 was published in 1972, probably in February.

http://home.earthlink.net/~mike.terrell/Sams-Index.html Is a chart by
year of publication. This information isn't in the Sams electronic
index. If anyone has any newer data, I would appreciate it.

http://home.earthlink.net/~mike.terrell/HWSAr.html is a list of the AR
manuals I have on hand at this time.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida