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SX-737 tuner AWE-043

A question to all following this thread.
The last test with the oscilloscope convinced me, to get one for myself. But which one is the best value for money for all the work on the typical HiFi Pioneer unit.
Would you still prefer an old analog like the Tektronix 2225 or better get one of the new digital oscilloscope?
Has anyone of you a digital oscar on his bench and is happy with it?
Don’t want to spent more than 200 -250$ without knowing if it’s worth it.

Every advice is welcome.
 
pa_200 said:
Got the Hameg HM205 today and a short introduction from my friend. Together we did some testing with the probe between T5 and F1, hocked up an R15. Then moved the Tuning wheel and every time we tuned in to a strong radio station, there was a small but noticeable change on the displayed signal. Was like a very small sinus wave.

What would you advice for further testing to check out the front end working ok?
Click to expand...

Did you happen to check the signal after F1? How about at Q4 and after F2?
 
We checked the way from T5 to HA1137 via R15 – F2 – R21. As I wrote yesterday, there was a very thin line and every time we got close to a strong radio station, there was a small but noticeable change on the displayed signal. But being honest, we can’t be sure with the tools we had, if the signal was good and strong enough.
That is the one of the reason for me to look for a better oscilloscope that can help better and in display more information.
 
I have a SX 450 without any FM/AM sound. I'm watching this post very closely to pick up any pointers. Good luck on your journey.
 
micrometer said:
I have a SX 450 without any FM/AM sound. I'm watching this post very closely to pick up any pointers. Good luck on your journey.
Click to expand...

You should have the best guidance with @Watthour and @zebulon1 joining in to help. Would be great if we both can get our tuners back to work again.

Like your hint with the Grumman F6F Hellcat, perhaps we are interested and/or worked both with military aircrafts.
 
I suggest to start by replacing the HA1137 in a socket. Then verify the voltages to the schematic. if that is fine then
You are going to need a plastic tuning tool to adjust the quadrature ( T5 bottom slug) coil for AFC (meter) centering,
Without a RF SG and a way to measure thd you are just going to have to live with it, by not being able to trim the quad coil ( top slug), step 15

Good luck
 
That might actually work. There is a video showing its features and construction:


If you are thinking of using that, an RF attenuator might also be necessary.
 
Last edited:
First success after several days waiting for the parts.

Got the IC sockets and HA1137 on the last day 2021. Today I hat time and carefully unsoldered the suspected HA1137 and cleaned the surrounding area. Put in a DIP 16 socket and checked that there is no solder bridge between the pins. With the new HA1137 in the socket, pins recheck and fingers crossed, first start on DBT.

WOW, Signal and Tuner where moving. What a relieve. Next on full power, first with headphone AND the tuner worked.
Great sound and I’m able to tune in lots of stations with strong signal and stereo light ON. Will continue work on the unit later.

@Watthour, is there anything I should readjust after the HA1137 change, or can I just leave it as it is right now?

Just for the record, that are the voltages with the new HA1137 installed, Function selected, Muting OFF (button depressed)
1 = 2,02 all vdc
2 = 2,02
3 = 2,00
4 = 0,0
5 = 0,0
6 = 5,5
7 = 5,5
8 = 5,5
9 = 5,5
10 = 5,5
11 = 13,50
12 = 2,2
13 = 0,0
14 = 0,0
15 = 4,7
16 = 0,0
 
The only thing that might indicate a need for adjustment is the function of the tuning center meter and "STEREO" indicator. Of course, any adjustment includes the risk that reception could be negatively affected and require a full alignment to restore operation.

If the tuning meter is centered when there is no FM broadcast signal being received (dead air) there may be no adjustment necessary. If it is not centered, the lower core of T6 could be adjusted to center it.

Also, due to the relationship between the HA1137 and HA1156, if the best reception occurs when the tuning meter is centered, and the STEREO indicator lamp turns from Off-to-On (not On-to-Off) at approximately the same range above and below the tuning meter center position, it would be best to leave it as it is. Otherwise, adjustment at the HA1156 could be performed to dial in the VCO to exactly 76KHz.
 
Hello to all following this thread.

The tuner works fine for me, at least what my old ears can hear. The signal meter moves when tuned in to a strong station nearly to maximum deflection and the tuning needle is centered with STEREO lamp turns from Off-to-On on after coming close to the “bold line” from both sides. Hope this will stay like this for the future and I can avoid a new tuner adjustment.

What caused the HA1137 to fail, I can’t tell. Maybe one of you can bring some light to this.

What has been done on that tuner board AWE-043, mainly all the well-known troublemaker replaced.

Q8, Q9 (2SA725) – Replaced with SA992
C28, C38, C39, C40 – Replaced with film, the light blue Sanyos where really bad with up to 99 ohm ESR
C25, C27, C50 – Replaced with new electrolytic
(Q5) HA1137 - Replaced with a DIP 16 socket and new HA1137 chip

Thanks to everyone giving my help and assistance during the last weeks.
IMG_20220103_145026.jpg
 
Since the tuner functioned before the power supply and other boards were serviced, it is remotely possible that some transient from the power supply damaged the HA1137, but there is really no logical reason to assume that - Just a guess. It seems just a bit too coincidental for it to be a random failure of the decoder.
 
I think you did a great job to get that fixed! I wonder if HA1137 failures are common. Really lucky that we can still find those.
 
The HA1137W FM IF Amplifier DIP16 is still available at certain places but they become rare from year to year.

It ordered a patch of 10 from a store in Poland/Europe, the price for ten was at bit higher than the price for a single one from another supplier. Better you have some spares than none if you need one.

One information to keep in mind. I live in Germany/Europe and the big radio stations have announced, to switch of the old FM frequencies over the next years, as soon as we have a full Digital Audio Broadcasting (DAB) coverage.

That again means, there will be no future need for the HA1137 Chip and the shops try to sell of their remaining stock.
Here is the link if one likes to order as well, and he ships to Amerika, Europa, Asien, Australien
https://www.ebay.de/itm/293858298075
 
That's actually a pretty reasonable price, except the the shipping to North America.
 
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