Brooklynwgtn
Active Member
get a spare for me Kev, ill fling you some money ;-)
The OFFICIAL MSM5540RS/M5540 Sansui Gx700 40pin IC Thread! NUDIES
- Thread starter trueno92
- Start date
johnhoef
Well-Known Member
Kevzep, I am very familiar with the STK amp module work around that is discussed elsewhere in this forum. I was confronted with this very issue, looking for a replacement for an STK power output module. The problem was cost! Building a discrete module to replace the STK proved too expensive, and my customer rejected the repair. I finally found two of those STK modules of the original style...NOT counterfeit. I paid $50 for each, and my customer was thrilled to have his receiver working again. I think in most cases these discrete replacement modules are not cost effective.
Are you sure you wanted to post the above in this particular thread?
Better here than in the STK-0050 thread
makes one wonder. Happy New Year John, Kev and the rest of AK
Happy New Year Rick!Better here than in the STK-0050 thread
trueno92
Active Member
nice to see this thread still carrying on.
BTW< its not the chip thats failing. Its the power going into the chip that is getting a bit out of tolerances and i suspect the voltage going into the chip is running high with the inline caps drying out.
What would be the next concern is the digital display off gassing and becoming not readable.
BTW< its not the chip thats failing. Its the power going into the chip that is getting a bit out of tolerances and i suspect the voltage going into the chip is running high with the inline caps drying out.
What would be the next concern is the digital display off gassing and becoming not readable.
I tend to share the concern over the longevity of the display tube itself, but these appear to be very good quality VFD's, and I've not seen one of this type yet that was failing due to bad segments or poor luminosity. Worth noting that Sansui used this same VFD on a fair number of models, including:
All G-x700 models
TU-719
7900Z/8900ZDB/9900Z
T-80
IIRC, the tube itself is made by Itron (now Noritake Itron) and they were known for high quality VFD's.
I'm intugued by the theory that power supply drift is inducing failures of the MSM6640RS IC, that would be a plausibe explanation for the sudden onset of these chips failing in the last few years. However, replacing the failed IC with a new one would probably cause a repeated failure in short order if the supply voltage was off spec enough to kill the original chip.
I more suspect a simple matter of the chip fabrication proces being such that an internal failure of the lead wires out to the package pins, or a failure of some portion of the chip die itself going bad, is occuring.
We are seeing the same sort of problem with many earlier small signal transistors going noisy as oxidation or other contamination is able to compromise the internal portion of the device. Failed bonding of package leads to the die is also an issue for older devices where thre manufacturing technology was not as advanced as it has become since the mid to late 1980's.
All G-x700 models
TU-719
7900Z/8900ZDB/9900Z
T-80
IIRC, the tube itself is made by Itron (now Noritake Itron) and they were known for high quality VFD's.
I'm intugued by the theory that power supply drift is inducing failures of the MSM6640RS IC, that would be a plausibe explanation for the sudden onset of these chips failing in the last few years. However, replacing the failed IC with a new one would probably cause a repeated failure in short order if the supply voltage was off spec enough to kill the original chip.
I more suspect a simple matter of the chip fabrication proces being such that an internal failure of the lead wires out to the package pins, or a failure of some portion of the chip die itself going bad, is occuring.
We are seeing the same sort of problem with many earlier small signal transistors going noisy as oxidation or other contamination is able to compromise the internal portion of the device. Failed bonding of package leads to the die is also an issue for older devices where thre manufacturing technology was not as advanced as it has become since the mid to late 1980's.
Doubtful that shipping it caused the failure, this IC just seems prone to age related spontanous "death". Could be it is overly sensitive to drift in the power supply - which tends to happen with age - or any number of other things. I doubt we'll ever establish a clear cut reason for why they fail. For the moment NOS replacements are still available from Ceitron via their own website and ebay.
I'd suggest to anyone who owns and really values a tuner or receiver that utilizes this IC in it's design to have a spare or two on hand while they can still be obtained. Without this chip working, you are left with a partially crippled unit.
The following are models that used it: TU-719, TU-919, all G-*700 receivers and the T-80. I believe that is the complete list, as it really only saw use by Sansui in designs from late 1978-80. I've no idea if any other hifi maker used it in a tuner or receiver design, but would be intersting to find out.
It is a specialized chip, which was fairly common in the era before highly integrated multi function MCU's were used in audio gear, but may not have seen much use. It is really application specific for use in true analog tuners featuring a tacked on digital frequency readout. Obviously, analog tuners fell pretty quickly from favor in hifi after 1980/81, which quickly negated the need for something like the MSM5540 in new tuner designs that were all digital. Leaves me to wonder if OKI even recovered the development and production cost, given it's very short time in use.
I'd suggest to anyone who owns and really values a tuner or receiver that utilizes this IC in it's design to have a spare or two on hand while they can still be obtained. Without this chip working, you are left with a partially crippled unit.
The following are models that used it: TU-719, TU-919, all G-*700 receivers and the T-80. I believe that is the complete list, as it really only saw use by Sansui in designs from late 1978-80. I've no idea if any other hifi maker used it in a tuner or receiver design, but would be intersting to find out.
It is a specialized chip, which was fairly common in the era before highly integrated multi function MCU's were used in audio gear, but may not have seen much use. It is really application specific for use in true analog tuners featuring a tacked on digital frequency readout. Obviously, analog tuners fell pretty quickly from favor in hifi after 1980/81, which quickly negated the need for something like the MSM5540 in new tuner designs that were all digital. Leaves me to wonder if OKI even recovered the development and production cost, given it's very short time in use.
Like @Sansuiman says, the transport likely didn't cause the failure. Although it is possible a solder joint or two going rogue may have occurred. If the quartz lock doesn't work, the 5540 has finally failed. If the quartz lock still works, it is possible something else has failed. There have been the rare instance that changing the crystal has brought a few back to life, but only a few. And of those, the quartz lock still worked before and it was just the display readout was "off" as in it still changed, but was the wrong readout. On my G-4700, I called it my "patriotic" receiver. The display was stuck at 1776.
Installing a 40 pin socket, and a new 5540 (from Ceitron) fixed it. I used a socket so there was no chance of heat damage to the chip from soldering it. The rumor is the cleaning of the etching agent couldn't be completely done because of the complexity and technology at the time. The residue from the etching agent continued to etch slowly as time went by and electrons flowing through the circuitry made it worse. I also still have a T-80 that works. It wasn't used very much over the years and that is why it still currently works. I just powered it on (I rarely use it) and it is still working perfectly.
Interesting info regarding the die in the chip failing due to residual etching agent. Where did that originate from? I haven't seen it discussed here at all, so is new to me, though within the bounds of plausibility. Of course, if that is the case, I'd expect even the NOS chips to have a reduced lifespan.
That was talked about a few years ago in many forums. I can't remember the specific forums, some over at DIY, and a few others whose names elude me. Many IC chips were way less complicated and the etchant could be flushed out well enough to essentially become inert. I'd bet that with new modern processes, this 5540 could be produced more reliably. Look at all the way more complicated chips being produced today with little to no etching problems. Even many chips from the 1990s are still going strong benefiting from the then "improved" processes since the 5540 was produced. Now a "simple" BJT/FET being NOS isn't really a problem. With them being unused, the tin whiskers haven't had electrons flowing to grow them. The 5540 would also not have the whiskers growing, but the etchant would still be "active" but not accelerated by electron flow. An NOS 5540 should last for a number of years, but probably at about half it's 40 yr lifespan (or less) as compared to a brand spanking new one. Every year we can squeeze out of these old units, the longer they stay out of the landfills. If my 4700 display goes belly up again, and there's no "fix" available, I'll still tune it in by ear and enjoy the music.
I picked up a g-4700 a while ago that had a display problem we thought was the 5540 chip. The frequency display would jump from the tuned setting to 189.3 mHz and back at random. Quartz lock light would also go off. Tuner drifted from the station it was set to. I bought a new 5540 chip from ceitron.com. Didn't help. Turned out the be the AN6821 chip on the F-3010 pre-scaler board. Once that was replaced, the receiver is now working like a champ. Original 5540 chip is back in the socket that was installed, and the new one is in the spare parts bin waiting for that rainy day.
The prescaler board divides the FM signal by 100, so you can disconnect the prescaler board output from the F-3000 display board and run a signal generator to the F-3000 board to check it. Also, the problem didn't happen on AM, just FM. Since only the FM signal is divided by 100, that's another clue that it's the divide by 100 chips. AN6821 scales by 20, then the 74LS90 decade counter chip is wired to divide by 5. Also can run a signal into the pre-scaler board, and check the output with a scope or freq counter.
The prescaler board divides the FM signal by 100, so you can disconnect the prescaler board output from the F-3000 display board and run a signal generator to the F-3000 board to check it. Also, the problem didn't happen on AM, just FM. Since only the FM signal is divided by 100, that's another clue that it's the divide by 100 chips. AN6821 scales by 20, then the 74LS90 decade counter chip is wired to divide by 5. Also can run a signal into the pre-scaler board, and check the output with a scope or freq counter.
crashdummy
New Member
No FM on Sansui G-6700 Everything works great but the FM. AM plays fine and the digital display frequency changes when you turn the dial and the signal display works also. FM is dead, no sound and no signal or display change when you turn the dial.
The FM display is locked around 189.4MHZ and still around the same after replacing the Chip AN6821 on the Pre-Scaler (F-3010 Bd). My first attempt at fixing 2/21.
I did have it looked at a shop in Portland Or and they had it for two months and gave it back and said they can't fix it. The only thing they did is replace the HA11225 IC in the RF BD F- 2988. From what I can tell is an Integrated Circuit RF/IF-Stage.
My understanding the ultra rare Oki MSN 5540 display chip or 6.5536MHz reference crystal oscillator could also be affect this also but mine seems to be working to me because AM working?
Any Ideas were I should go from here minus needing a signal generator would be Awesome
The FM display is locked around 189.4MHZ and still around the same after replacing the Chip AN6821 on the Pre-Scaler (F-3010 Bd). My first attempt at fixing 2/21.
I did have it looked at a shop in Portland Or and they had it for two months and gave it back and said they can't fix it. The only thing they did is replace the HA11225 IC in the RF BD F- 2988. From what I can tell is an Integrated Circuit RF/IF-Stage.
My understanding the ultra rare Oki MSN 5540 display chip or 6.5536MHz reference crystal oscillator could also be affect this also but mine seems to be working to me because AM working?
Any Ideas were I should go from here minus needing a signal generator would be Awesome
If there is no FM signal or audio output, there is a problem with the tuner before the MSM5540 comes into play. Failure of the MSM5540 chip will not cause failure of output (signal and audio) from the tuner, it will only effect the digital display readout and FM quartz lock functions.
I'm no tuner guru, so will defer to others here to offer advice on where to begin troubleshooting the front end and IF stages. With any luck though, the 5540 chip will not be in need of replacement.
I'm no tuner guru, so will defer to others here to offer advice on where to begin troubleshooting the front end and IF stages. With any luck though, the 5540 chip will not be in need of replacement.