sx626 tuner woe

J

john stumpf

Super Member
ive been going through this thing doing a recap and new silica and its developed a problem on the left fm channel. it played reaaly nice when i got after cleaning all the switches. i almost didnt do anything to it except i know it was just a matter of time before it would give trouble. i rebuilt the power supply and then moved on to the equalizer board,not very difficult at all,but when a fm stereo check was done the left ch, was weak and distorted. ive even removed the installed parts and checked every one and all the pinouts on the equalizer board,to no avail.in frustration i dug out a old digital tuner and plugged it in to AUX. and all was right in the world. the next step was more d5 on the gang switch s-1. still no luck. i ohm'ed out the wiring through the gang switch to in on the equalizer board and the cr board .03 ohms it doesnt get any better than that. so to my mind it must be the tuner and its something that just happened. right channel is great and i have a stereo indicator light.due to its sudden onset i was suspecting the ha1142 chip but all the voltages seem to be normal or very near normal. not sure how to approach this but ha1142's seem to be made of "UNOBTAINIUM" but im not sold on it's being the cause. its a '73 version with an awe-031 tuner
 
i do not have a schematic for awe-031. Anything else use this awe-031? I have no spec for the HA1142 either.
Anything to align?
 
not that im aware of.i got the schematic from hi fi engine the data base here doesnt have the later version. no mpx signal generator on hand,but will do a front end job in the am.
 
been reading a bit, you suppose it could be the low pass filter? i suppose it would be easy enough to jump temporarily as a process of elimination. no you are correct it does have a ha1142.i dont suppose anything else will work? i sure do hate to be mucking about in the mpx without a signal generator. couldnt even find a 1142 data sheet online
 
Sure, try to short out the o/p low pass filters to see if they are lossy.
FYI, I have a HP 8904A to use as a stereo multiplex gen. You can get them for around $200, make sure you get the later model and with the 002 option.
I can not seem to find anything that used the HA1142, maybe I am losing it :)
 
its a no go on bypassing the low pass.s.s.d.d. as theres not much else in there i can only guess at the ha1142. qx949 has the 1142 chip.NOT the 949A
 
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Can you probe pins 10 & 11 for signal? If levels are the same at those points, the HA1142 would probably be O.K. That would be a good thing. If the levels are different, start looking at the surrounding components, like C32/33 and R30/31.
 
10-11 are11.2 volts the .47mf caps are new wima stacked films, in on r33 andr32 is 42mv out to 14 and 16 is 3,1mv. its got me stuffed.
 
QX-949, there you go, so HA1142 is basically the old circuit put into one package.

T7 and T8 are traps, can not short them out.

Q7 pins 10,11 = 11.2V seems high to me but without a spec I can not be certain.

Tune to a known strong stereo signal. Scope the o/p's R32,33, try adjusting per the procedure do not worry about L only modulation, try to peaking T7 for maximum out on both channels. Do not worry about T5. Mark where VR1 is set, try adjusting VR1 see what that does on the scope.
 
it has progressed from bad to worse as my signal generator has developed a frequency mind of its own and now appears to be d.o.a. as a result the alignment is so far out i dont think marconi could align it! looks like i'll be on ebay looking for a reasonable replacement.thanks for all your support."the thrill of victory and the agony of defeat" i'm temporarily burned out.
 
I like the marconi reference.
the thing is about these tuners and general troubleshooting, is that you need some really good test gear in order to sort out what's up. without the gear it becomes a guessing game as to what is out of wack. to bad we are not down the street from each other or I'd like to help you out with the tuner stuff. Rent my lab for a case of beer :)
I agree getting another tuner pcb is a good idea if you want to save it. A royal PITA option = sorry.
What SG are you using?
With test gear, in order to repair it, you need more test gear. In the old days us hobbyist were screwed, now with cheaper old HP stuff we can get by without a huge expense.
With my RF SG, HP 8656B, I have a spare for parts because many parts are out of production. It costs more but it buys you time. iirc I got the spare from Israel, ~ 100 + 100 for shipping. best that one can do imo. A working 8656B you can get for 200 on a good day, but they are expensive to ship. i see lots of them on ebay.
Israel has a ton of HP gear which they are unloading because of eol for service in military requirements. Agilient stopped supporting them long ago and now the mil labs are unloading them at auctions.
HP had the 8656B as the economy model at $6300 + $950 for the 10MHz oven osc reference.
It is full of 7400LS TTL. The later production models used the green 7-seg LEDs, I have the older red model, it works fine, it was from the Motorola dev lab in Toronto.
 
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national vp8177a,got it for 60$!!!! unfortunately the seller has since found out he can flog the stuff on the bay for 10 times that and unless i want to pay he wont deal anymore.that generator got me through 13 alignments so i got my money's worth.its just a damned shame it gave no warning. it was the last set i was going to do as the prices have skyrocketed on ebay as well as shipping under the global screwing program.it was fun while it lasted! ive seen the israeli stuff and as reasonable as it is, the customs here will charge 30-50% of the declared price unless the seller is willing to indulge in creative writing on the declaration its just too hard here.im not a true tech like you folks,i brought three over here with me and gave two away to my friends after 6 mos the gifted 939 developed popping and static i discovered ak and the rest is history. ive got a awe046 fron a sx636 but its been robbed of a filter coil it shares identitical mounting holes and is pretty much the same tuner as the awe031 except it uses a ha1156 instead of the 1142 ive been studiying the schematics and the difference data and at first inspection it appears its a "bolt in" excepting the fact that id have to up the resistance of the signal path through the cr board.just a thought now as there are no awe31's on the bay and the early 626 tuner is totally different. if you were saddled with this dilemna and no signal generator.how would you get the local oscillator back to where it needs to be? ive tried but the closest i can get is terrible reception and no stereo light at all. i really hate to give up on it as it runs counter to my nature.
 
I've got a HP8657A RF gen, and a National VP7633A Multiplex Generator. The HP is solid, and I got it for next to nothing, I have another one under the bench with low output which I'll repair one day when I get time. Also have a Marconi 2018 RF gen as well, got that for next to nothing as well, it had a dead transistor in the frequency divider circuit, too me a long time to find that, but it was great to get it going, its my backup.
The VP7633A multiplex generator is actually really good, if you want to put noise through the unit to test frequency response, it has the preemphasis and everything. Having said that, I am terrified it will fail because as hard as I try I cannot find a service manual for it.
I have the Sencore SG165 if everything fails as a last resort!!
I have seen the HP8657 for pretty cheap in the USA on the bay.......

I like doing tuner alignments so I've invested time and money to be able to do it as there are very few if any techs in New Zealand who actually do it, I get quite a lot of them to align and repair...
 
I guess you are going to have to find your test equipment locally, as I did for mine. You have to be patient, watch and wait for the right opportunity, hopefully it comes to you.
As I said it is pretty hard to troubleshoot tuners without good equipment.
That is why I stayed away from the National equipment, no service manual = no buy, period.
 
rcs16 said:
I guess you are going to have to find your test equipment locally, as I did for mine. You have to be patient, watch and wait for the right opportunity, hopefully it comes to you.
As I said it is pretty hard to troubleshoot tuners without good equipment.
That is why I stayed away from the National equipment, no service manual = no buy, period.
Click to expand...

Good call on that!!
My Multiplex gen has been okay, had it for over a year so touch wood I'll get a few more miles out of it before anything fails....I might give it a re-cap hopefully that might give it a bit more life...
 
yep thats the guy. apparently hes had a price reduction.that 8177a was sure a breeze to use too. what you all must realize there are no guarantee's as to whether it even works or not when you buy here,you add the shipping to the us and it can be expensive exercise in futility. its all "as is" still.... most of his sales are make offer, i'd offer half and see if he bites. yep just down the road about 100 kliks im even going to the va in manila tomorrow.
 
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Simple enough to test out a RF SG for broadcast radio, use a portable AM/FM radio if you are travelling, connect an antenna to the o/p RF jack of the RFSG, simple as a few loops of wire from centre pin to ground. usually a "BNC" or a "N" used on a RFSG. set RFSG to any freq, i.e. 98.1MHz FM, modulate at 75Khz deviation, rate can be any of the default settings 400Hz,1KHz, set RF level as high as it goes, ~10dBm. This tests basic operation of the RFSG.
then once you get the radio tuned-in to the RFSG carrier, if it works properly, then start reducing the RF level till the radio comes out of quieting. This tests the attenuators, RF level to take the radio out of quieting should be way down there, -90dBm I am guessing.
You can do the same as above except using AM/CW modulation in the AM/MW band of the radio. modulate AM at up to its max of 99% usually.

Good Luck
Rick
 
rcs16 said:
Any info on that VP7633A ?

Well look what I found, just down the road from John's place, I hope :)

https://www.ebay.com/itm/Panasonic-...633A-Multiplex-Stereo-Generator-/391522237453

I have $204.80 Standard International Shipping to Canada
International items may be subject to customs processing and additional charges.
Item location: Taguig City, Philippines
Ships to:Worldwide

and another one
https://www.ebay.com/itm/National-Panasonic-VP-8177a-VP8177a-FM-AM-Signal-Generator/401164073638?_trkparms=aid=222007&algo=SIM.MBE&ao=2&asc=52475&meid=998cfc0e6249459fa62c7564676db36f&pid=100005&rk=1&rkt=2&sd=391522237453&itm=401164073638&_trksid=p2047675.c100005.m1851
Click to expand...
I have the VP7633A, its only a Multiplex generator, no RF generator onboard that model.
Its pretty cool as it has the ability to take an external input, has the pre-emphasis so I can check frequency response of tuners on my FFT audio analyser.
I have bought from that seller before, in fact I bought my 7633A from this guy.
The gear works, he's quite helpful when it doesn't, he sent me a whole parts unit for my HP8657A as the one he sent me in the first place has a output level issue, and since he sold it working, he shipped a parts unit, and funny thing, the parts unit worked perfectly after I replaced the exploded tantalum cap I found on one of the boards....So I have a whole spare unit I will fix one day.
 
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