ASTRO-SONIC Speaker output problem

Hi I recently acquired a mint 1965 Astro-Sonic at a garage sale for $50. One problem the output from the left side speakers is very weak compared to the right. Thanks for any help anyone can give me .. nddpm@msn.com

Hello,

you might want to take the back off your stereo, Take a look at your amplifier, and see
if there is a balance knob. There is one on mine, and you can adjust the balance on it.
If your left side speaker is weaker than your right, I think it would have everything to
do with the way the balance is set. let me know if this helps.

Do all audio sources have this problem ? By the way, the balance knob on my astro sonic is located between the two transformers. It's fairly safe to be prowling around inside these units while there on so you can listen while making adjustments but if you have to crank up the volume knob really high to compensate the amp has a problem.

You shouldn't have to fool with the balance control. That is set at the factory. If the weak side is with phono only, replace the cartridge. If it's weak in all modes, phono, radio, aux., it could possibly be the speakers. Hook up a set of extension speakers to verify that. If it's still weak, you may have to replace electrolytic capacitors, resistors, transistors. I would do a Cap job first, that usually solves most problems. Also, check the rotary knob for the phono, radio, aux modes. I have one with dirty contacts and had to rotate back and forth to get both channels working. I'll take it apart one day and clean it.

If both channels work when using radio or external Tape/Cd player, it's most likely your cartridge. There were a few instances where I had to replace the small driver transistors.

BobbyB
Tucson, Arizona

I have about the same problem with mine, though sometimes the audio on the left side wants to cut out completely now and then. It's a Model 1P3724, Cherry finish, Serial 4311569, Chassis R22010 (I believe this is right, as I was looking at it upside-down and backwards in a mirror), Changer W801/01/00, not sure at the moment what Run # it is.

Also, it does have the RCA-style jacks on the back for tape/CD hook-up. When I've hooked up my portable CD player to it in the past, I've had to turn the volume all the way up on the CD player, as well as quite high on the main cabinet. (I've been able to "match" the volume on the CD player to the volume on my RCA Victor console without any problems.)

Hi.
I have an Astro Sonic 1RP638 with a tuner chassis No. 204-03-00 and I've had the same problem, left channel. I bought another tuner at eBay (actually 2 tuners) but I'm trying to fix the otherone with a technician.

The suggestions I've had from the web-experts on this specific tuner are:

ONE:
On the audio board which has components numbered in the
200's on the circuit board a good possibility would be C-207 or C-214.
These are 5 mfd at 25 volt electrolytics and feed the audio out to the
tone switches, volume control and onto the output jacks that go to the
power amplifier. The only way to accurately check these campacitors is
by using an ESR meter, they will check good with a VOM or Digital Ohm
meter and still be bad. C-207 feeds Ch-1 and C-214 feeds Ch-2. These
are inexpensive parts and I'd just replace both of them.

I have a Magnavox Component Receiver which uses the R-204 chassis that
was used in some consoles and it had the same symptom you're
describing, turned out to be one of these capacitors was not passing
audio. The R-204 receiver is very similar to the R-207 except it has
the power amplifier mounted on the tuner chassis.

TWO:>IN ADDITION... If those 5MF/25v's are failing, then
C207,214,209,213,217,215 are invevitably going to fail as well, being
all the same value. I'd also replace the speaker coupling caps
C237,329, 200MF/20V to be on the safe side, a 470MF/50V wouldn't hurt,
and give a bit more punch to the bass. Unless you like going back into
the chassis over and over, a total re-cap of all the 'lytics is a good
option. I assume the output level though the tape out jacks is equal,
but when I come across a vintage piece at the shop I always suspect
old 'lytics. Signal Tracers/Injectors are invaluable for these kinds
of troubles to track down the culprit.

THREE:
To quote my Magnavox Service Manual:
"It should be remembered, however, that the output transistors,
although identified in this manner must still be replaced in matched
pairs."
For the R204-03 chassis the output transistors Q301,2,3,4 are all PNP,
and a matched pair of 170407-1 is the proper identification number.
ECG/NTE 121's are suitable replacements. I'd also check the bias
resistors and replace the output coupling caps to be thorough.

As I told you, my tuner is still being repaired so the only thing I can do is pass you the suggestions I've received.

I've had luck contacting people who are selling other Astro Sonic parts on eBay, asking them if they have a tuner and I've manage to buy 2 of them.

If I can fix my tuner, I'll let you know which part had to be replaced. Right now the technician told me it's the output transistor ..... let's see.

I hope this helps,

luigi_alegre@yahoo.com

I would replace ALL the Electrolytic Caps first. That may solve all the problems. I've had units with the caps popped out on both ends. A complete Cap job brought it back to life. I also had several instances where one of the small driver transistors failed. They're located in the pre-amp section where all the inputs (phono, radio, aux, etc.) pass through. Sometimes that section is mounted on its own little board elevated from the main board. There may be at least three pairs.

Definitely get an NTE/ECG catalog or the CD-Rom. You can cross reference all those parts, and are still available or a suitable generic substitute, less than four bucks apiece, since I last did any amp work. If your radio and any external inputs work fine, narrow the problem down to the cartridge, wiring, driver transistor. The larger output transistors are usually ok, but they can fail, too, somewhere between 10 and 20 bucks. I can't remember right now. It's an inexpensive fix.

This doesn't sound like major surgery, and I'm sure you can trace those little gremlins. Do a process of elimination after the Cap Job. Thank goodness the power transformer is still intact, that's where the bigger bucks would kick in. Good luck to you guys.

Oh, by the way, have a safe and happy holiday season. I've been so busy and miss talking to you guys. -BB

Bobby Basham
Tucson, Arisona

I don't know if this would happen to make sense, but from what I understand, having read from somewhere else, (this is in general for all stereo consoles as well as Maggies)...would one side have more bass/treble than the other ("bass drivers") (when turning the balance knob from one side to the other), or should it be equal on both sides?

If one side has more bass than the other, it is usually a bad speaker.

But some units with a main unit and a satellite speaker put a single woofer fed by both channels in the main unit.

In regards to my earlier post of Dec. 3, 07 (I was unkowingly signed in as 'Guest' when I posted it), concerning a speaker output problem with a Model 1P3724 Maggie.... The left speaker tends to cut out sometimes, but it only happens in the Phono mode; all other modes both speakers work fine. I thought it might have been the cartridge going bad, but I ended up replacing the changer entirely due to motor going bad. (The changer that was in it was a W801 series; the one I just put in is identical, except for colour, is a W624 series; both with the fishhook stabilizer arm, flat 'domino' 45 adapter, and molex audio connection instead of the RCA type.) Even after changer replacement, the left speaker is still cutting out sometimes. Appearantly it wasn't the cartridge after all, since I'm not using the cartridge from the previous changer. Again, it only does this in 'Phono' mode; all other modes both speakers work just fine. Cap need replacing, or the audio wire between changer and chassis going bad?

Just a Guess-How about the "mode" switch contacts ? Ron Rich

I agree with Ron Rich. I do have a couple of consoles where a channel would cut out if you rocked the "mode" switch back and forth. Dirty contacts. --BB

Bobby Basham
Tucson, Arizona

stereoplayers wrote:In regards to my earlier post of Dec. 3, 07 (I was unkowingly signed in as 'Guest' when I posted it), concerning a speaker output problem with a Model 1P3724 Maggie.... The left speaker tends to cut out sometimes, but it only happens in the Phono mode; all other modes both speakers work fine. I thought it might have been the cartridge going bad, but I ended up replacing the changer entirely due to motor going bad. (The changer that was in it was a W801 series; the one I just put in is identical, except for colour, is a W624 series; both with the fishhook stabilizer arm, flat 'domino' 45 adapter, and molex audio connection instead of the RCA type.) Even after changer replacement, the left speaker is still cutting out sometimes. Appearantly it wasn't the cartridge after all, since I'm not using the cartridge from the previous changer. Again, it only does this in 'Phono' mode; all other modes both speakers work just fine. Cap need replacing, or the audio wire between changer and chassis going bad?

It's been a few years, but eventually did find out why the left channel would want to cut out while in Phono mode. The solder cracked/loosened up on the audio connections on the chassis. Got out the soldering iron, some solder, and everything works like a dream--no more 'cut out' problem...

Good for you! Cold solder joints can be a pain. Sometimes I take a tooth pick and press gently around the circuit board or use the continuity feature on my meter to discover little gremlins.

Would you have a pic of a W624 series. I have manuals for the W620-W622 but don't believe I've seen one of those.


Victories, though small, are still great! --BB

Bobby Basham
Tucson, Arizona