Technics SA-5170 Repair Journey - No FM Stereo

This Technics SA-5170 receiver is not receiving stereo FM. I'm hoping I have enough skill to find the cause and get the receiver working in stereo again.

[@kf4hnf]

Hi Jim I used to work on this stuff long ago and it sounds like you have a weak signal. If your shop is in a basement or building with metal siding. The signal won't be strong enough for the subcarrier to trigger the decoder. The mute circuit mute's the weak signals so you don't hear the static. Try running an outside wire antenna about 10 ft. off the ground and see if that helps. If not try using a signal tracer or scope to find out where where your losing the signal. ether the RF or IF amp. Lawrence.

[@martyjewell5683]

This was a sweet budget+ receiver from the golden age. Offering all the basic features and 25wpc. Tape, aux inputs and a nice look. For a moderately powered "vintage" system driving EPI-100 speakers this could fill a moderate sized room with clean sound. Got my girlfriend an SA-80 receiver in 1981 and was surprised by the quality and performance. Very interesting video, thanks.

[@mashtunk101]

I've got one just like the one he's working on and it's certainly powerful enough to fill more than just one room. Pretty powerful in my opinion for only 145 watts. Picked mine up at a vintage stereo shop, fully restored for $280. Extremely happy with it.

[@martyjewell5683]

@@mashtunk101, the receiver in this video is only 25wpc. If you have a 145 watt unit, it is not an SA-5170. Google Hifi Engine for correct specifications. This SA-5170 is a budget+ model. It's a fine component, but it ain't no 145w powerhouse. Though, paying $280 for a fully restored 145wpc receiver is quite a great bargain. Kudos for your sharp purchase. I picked up fully restored (sonically and cosmetically) Ohm Acoustics model H speakers a few years back for $275. These speakers sold in late 1970's for over $700 a pair and I paid $275 for two, a freakin' steal.

[@hanson-david]

Hi, just a note to explain the principle of FM Stereo. The explanation at 20:00 is incorrect. This is frequency division multiplexing (FDM) and not time division multiplexing (TDM) as in the video. There is no switching happening here. In the frequency spectrum of FM stereo transmission, the signal below the 19khz is carrying (L+R) signal. Then either side of 38khz suppressed carrier is (L-R) signal. The mono reception is only interested in (L+R). But the stereo receiver does an addition and a subtraction to get L and R separately. ( L+R) + (L-R)= 2L. and (L+R) -(L-R)=2R. The moment the receiver detects a 19khz signal, it knows it is a stereo transmission. The mono transmission does not send the 19khz.

[@nathanokun8801]

Even though Jim has very little experience with solid-state equipment and stereo machines especially, he can figure out ways to get around problems without major surgery (if possible). Impressive! True competence...

[@harryshector]

Since “cutting that diode restored the stereo operation to the receiver, I’d suggest you check that diode. If it’s ok,then whatever is supplying the signal to the line that diode is in is next. You’ve found a problem, but you haven’t fixed it.

[@hestheMaster]

You should get a regular old fashioned TV antenna with two segmented antennas (dipole) and with 300 Ohm terminals to connect it to vintage equipment ! If you're in the basement Jim an extension of twin lead to reach an outdoor window should help with picking up many FM stations!

[@timcorner2821]

I think you need to adjust with the adjustment screw ( VR-302 or VR-302 on schematic) till you see the fm stereo lamp light up.

[@user-oo2lx1es3q]

I have a "Technics SA 200" and a similar situation, only "stereo" is on all the time. And when you switch to "auto", the signal disappears altogether. Thanks to your video, now I will know where the "dog rummaged". I like and subscribe to you. Thank you for your help.

[@yusdiy]

I admire your patience sir. Whether its a success or fail, it doesnt matter.Thank you and keep up the good work.

[@scarswebare6999]

Hey Jim, question.... Happen to know what a Dolby FM Broadcast Unit Model 334 with the Type-B Cat No. 66 card in it would run these days? It's all but impossible to find them and information is minimal with the exception of the original documentation.

[@rick601a]

Looks like the main problem was weak signal. You really need an am fm stereo test set to preform service on this issue. Not seen much failures in this series of units. Pretty straight forward design and about as basic as they got. But a test set is a must for getting good signals and troubleshooting

[@2010stoof]

I am looking buying one of these. Sa-500 Seller says something wrong with tuning. Only goes to the right and won't go left. He said something about wires and pulleys. Is that an easy fix? Unit was recapped.

[@sajusebastian4991]

Hi,Which is your ESR meter? Thanks

[@davidblue7228]

Need help with a sa-101 model the right channel dosn't work only a static sound? Any ideas?

[@volodymyr_gudz]

I have a JVC FX-1100. Any idea what to do? Same problem. No stereo.

[@felipeengelmann9636]

Hello man, I recently acquired one of these in a garage sale and it works almost great. Only the right speakers work, when I go left it goes quiet, so I changed the little fuses in the back, but it didn’t fix the problem, so I hooked all 4 ceiling speakers I have on the right. Can that cause long term damage? How to check what else could have caused the problem with the left speakers? And then my second question, which is kind of even more important, when I run it on volume 3 or 4 for over 1h it starts to smell like if it would catch on fire. What you recommend me to check first?

[@tf7274]

When I buy anything used, I spin every knob 40 times. Flick every switch 40 times. No shortcuts. I had a completely dead Technics that was quiet because of the speaker switch and tape being dirty. Loading 4 speakers on one out will cook it at high levels.

[@coltronex]

Two words,"Outside Antenna" Jim,rabbit ears no good!

[@jasonmushersee]

been a long hot humid summer the fm stopped working on my '91 silverado stock radio could just barely hear strong stations at full volume. am worked normal. then end of september everything works normal again

[@opus1952]

Jim, just a suggestion, clean the switch and check that the indicator light is actually working. Those old lights pop all the time.

[@terrycard6775]

Glad it's not my amp

[@ruawhitepaw]

There is no back and forth switching in FM stereo detection. Rather, the baseband mono signal is the sum of the left and right channels, and the stereo signal is the difference between them. It's the same principle as TV colour. The stereo difference signal is modulated at 38 kHz, using AM with suppressed carrier. The 19 kHz stereo pilot tone is used to recover the exact frequency and phase of the 38 kHz carrier so that it can be reconstructed and demodulated. That's what the "phase demodulator" is doing.

[@randomsteve4288]

Actually modern MPX stereo decoder IC work along the principle of synchronous detection and this involves treating the composite signal as if it was encoded switching between L and R channel at double carrier frequency. And if I interpret the datasheet of Matsushitas AN363N correctly it is using a synchronous detection type mpx decoder.

[@ruawhitepaw]

@@randomsteve4288 Wow, and that *works*?

[@JosephLorentzen]

Looks exactly like a SoundDesign radio I repaired

[@sarahhoward9081]

I have a technics sa 6000x that used to sound wonderful. Been in use for many years. It has one speaker dead. All that's on it is a little white noise. The other speaker on that channel is fine. I opened it up a while back and was so overwhelmed with the complexity of the circuit I basically gave up. I measured the voltages on the 4 transistors and couldn't find any fault with them in circuit. Can anyone help me?

[@hestheMaster]

Clean those pots especially the selector switch. Get a schematic off Ebay. That would be the next thing to do. I'd search KZbin if anyone has had a similar problem on a Technics receiver too, not necessarily a 6000x ( i.e. 5600X). Without a roadmap schematic I wouldn't even know what to do either except for the basics. Definitely well worth fixing it in any case.

[@sarahhoward9081]

@@hestheMaster I cleaned all the pots. They were very dirty. Numerous searches have turned up no similar problems. If the transistor was the problem wouldn't that whole channel be dead? It has a very odd speaker arrangement where you can flip a switch and change your speaker cables around for a different sound. It's called stereo 4ch matrix, and in that setting there is 90°phase and 0°phase. There is also 4ch discreet. I'm guessing that's 90° out of phase and the zero means they are in phase? Way more complex than anything I've ever worked on. Too bad the old tv radio repair shops are all gone. The schematic may as well be in Japanese, in fact I believe it is. It's like trying to decipher ancient Egyptian hieroglyphs. I cant suss it out.

[@hestheMaster]

@@sarahhoward9081 Sounds like you need to contact xraytonyb on this one!

[@dgillies5420]

THATS NOT HOW STEREO RADIO WORKS. At the base channel frequency (e.g. 104.1 Mhz) you have channel X=chanA+chanB (mono) in a 200 Khz band For a stereo station you have a 2nd signal of Y=chanA-chanB channel modulated 200 Khz higher (e.g. 104.3 Mhz). The receiver recovers stereo by X+Y = 2A, X-Y = 2B. If it can't pick up that 2nd signal 200 Khz higher, no stereo. So you will never see a stereo channel at 104.1 and 104.3, for example, since the 104.1 channel will be using 104.3 for its A-B signal. Happily, this scheme allows a Mono receiver to play the stereo station by tuning to 104.1. And when you hit the "mono" switch on your receiver it siply stops decoding the channel 200 Khz higher and plays the regular signal through both speakers.

[@samsokolowski0140]

Nice

[@gd2329j]

Low signal warning ? So you don't fix a working unit next time use your stereo generator !...

[@StillCloser]

OMG The way he 'explain' how FM stereo works, around 19:50 is completely wrong, kind of hilarious...

[@terrycard6775]

Useless

[@user-nq4eq5fn7j]

Lovely 😍💋 💝💖❤️