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disconnected

@snet.net

Accuphase T-105 FM tuner schematic download?

Anyone know where I can download one of these? One came into my shop this morning. Low sensitivity, open coil on the signal/multipath meter. Takes about 75dBf of input to get close to decent quieting. A schematic would be helpful. Hifimanuals lists one, but it's actually for the T-100.


disconnected

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So far, the meter problem was a defective D'arsonval movement. The manufacturer forgot to solder the bottom spring to the armature connection. Methinks this meter never worked from day one. With 10 power dual loupes, tweezers, a tiny strip of cellophane tape (to temporarily hold the spring where I can get to the inner solder point) and a needle thin soldering iron tip, I managed to make a perfect repair, attaching the meter spring to the armature and restoring functionality.
The next step was meter calibration. I chose to lock in the low and high end of the scale for most absolute accuracy, calibrating in steps from 21dBf, 40, 60, 80 and 100dBf. For the most part, the metering is surprisingly accurate. Then I calibrated the modulation metering (neat feature for a consumer tuner), using a spectrum analyzer to confirm the bandwidth coming out of my HP RF generator as +/-75KHz and setting the meter accordingly.
Sensitivity problem was a bad cable. I did peak up the RF stages for 3dB improvement in gain. Tweaked the phase response of the IFs for .02% THD bottom. Tuner seems to work great and audio response is relatively flat to 18KHz then drops about 40dB in the next KHz. Just finished aligning the LPFs on a spectrum analyzer and lining up both channels with the stored curve.
Pretty nice FM tuner.

daveinpoway
Premium
join:2006-07-03
Poway, CA
kudos:2
Accuphase makes pretty good equipment.


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Yes, and very impressive selectivity in narrow IF mode. 100dB alt channel. Even the local 50kW rock station down the road is tamed nicely and I can listen to 2nd adjacent with no interference. I counted close to 190 copyable FM stations up here on the mountain with a turnstile antenna on a mast.


ArthurS
Watch Those Blinking Lights
Premium
join:2000-10-28
Hamilton, ON
reply to disconnected
With all the "disposable" electronics these days, guys like you are becoming a rare breed. Wishing you a busy 2013 fixing gear that still "keeps on ticking"!


disconnected

@snet.net
Yes, we are becoming a rare commodity these days. I tried running a business like this forty years ago, but the competition was stiff. Today, I have little competitors. That's why they call us the amplifier experts.
Next item is an Akai GX77 which had been butchered by a previous owner. Numerous problems, including drive belt wrapped around support standoff, the rod that actuates fwd/rev slide switches off the track, a worn GX head! I managed to salvage it by moving a good head from the rev head block to the fwd block, and fixing the other problems. What a jigsaw puzle!


jrs8084
Premium
join:2002-03-02
Statesville, NC
kudos:1
Reviews:
·AT&T U-Verse
There is an Akai GX77 sitting on a rack in the other room. I think it has a reel of Pink Floyd The Wall ready to play. It probably hasn't been used in 8 years.

I don't know how well it compares, but I often long for my old Sansui 9090 receiver.


disconnected

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I remember the Sansui AU-999 with some fondness.
I myself have an Akai GX747dbx that I purchased from Japanese Stereo Mukashya in April 1984. It's still like new and works like new. One of the best decks Akai built.
Problem now with Akai servicing is lack of parts. The company went bust in 1999 with some bookkeeping skullduggery making $3M disappear. Some Singapore-based holding company bought them, but I see no focus on vintage gear. Mostly modern synths and televisions.
The GX77 is a somewhat shakey design. It's obviously a consumer deck built for light use. The mechanisms are crammed tightly together, with multiple layers of chassis, which makes for a service nightmare. I'm almost done with it, as I'm in the reliability testing phase to see if anything breaks, before I put the panels on and tell the customer it's ready.