Help with diagnosing faulty LCD on Becker CDR-220 car radio/CD player

[Valden]

Thanks for taking a look at this.

My 21 year old Becker CDR-220 suddenly stopped displaying all characters on the LCD of the removable faceplate. Other than this, the faceplate and body work properly. The buttons on the faceplate, the LED backlights, radio, CD - everything.

All contacts cleaned. No change.

All faceplate circuit board components checked. Seem OK. One dodgy-looking solder joint for a capacitor re-soldered. No change.

The pictured PCF8578 LCD driver IC seems OK when probed for appropriate terminal voltages and frequencies and continuity with the board, but with one possible anomaly. Column driver output 30 is inconsistent. All other row and column outputs show 2.4V (below VDD supply voltage of 4.6) and 2.25kHz. Column 30 is 0.08V and 0Hz. Perhaps it’s not connected? I’m checking.

This fault was instant and complete, so I don’t think the elastomeric connector strip between the board and the LCD is the cause. It’s been cleaned (problematic, I realise). No change.

What should I do next?

Replace the PCF8578? Or should I remove the radio from the dash and look for a fault in it? It could be that I2C bus data is not reaching the faceplate.

Also, how are these LCDs grounded? Via contact with the bezel? Or not at all? I can’t identify a path to ground, though there is a contact pad on the board for one of the bezel’s twist tabs, which is connected.

Thanks for clues and advice. Please don’t say, ‘Get a new radio.’ Heresy! 😄

[cantata.tech]

It's going to be a challenge.

I guess you could look up some of daves old videos and try to bypass the chip entirely and see if you can operate the actual display directly from a uC.

I'd be looking for spare parts about now on an online marketplace.

[Valden]

You’re right Cantata. It is proving to be a challenge.

I’ve continued with checking the circuit board of the removable faceplate and everything seems fine.

I found the contact pad that delivers I2C data from the radio and probed for frequency. It’s intermittent and variable, which might be OK, or might not be. I think it’s time to pull the radio out of the dash and start looking inside.

I’m going to start a separate thread, seeking help with identifying another IC on the faceplate board; a 36 pin IC (18 pins each side), marked NEC 1299 662, then 0128K3006. It’s shown in the full board pic, above. I can’t find anything on this. Strange. Clues appreciated.

Rgds, Valden.

[Runco990]

I'm afraid this may not help much, but download a service manual for it or similar Becker.  I have 2 traffic pro's.  The displays began to fade away some time ago.  What I found out is that the LCD bias voltage was faulty or no longer enough.  There is a resistor on the faceplate that sets it.  In my case, I breathed new life into it by jumpering it to get a crisp display again.

If nothing else, you can try that to diagnose if you lost the driver IC or just the bias voltage.

And yes..... Nice Radios. 

[Valden]

Thanks for your suggestion. I will follow up on this.

From the photo of the whole board in my first post (I can take a better one if needed, along with the other side), can you point to which resistor you think might be the one to focus on? Am I right in thinking you bypassed it, to raise the voltage going to the LCD?

Some extra information from tests yesterday. If I put the LCD glass on a light box, I can see that segments of the display are activated by using my multimeter probes in resistance test mode. This works with the red probe on the left-most contract and moving the black probe over others. Then I noticed segments would activate by using only the black probe. Very little voltage is needed, it seems. Fascinating.

[Valden]

Here's the latest on my diagnosis of this Becker CDR-220 car radio/CD player, with an faulty faceplate LCD.

I've carefully assessed each of the row and column outputs from the Philips PCF 8578 LCD driver IC. As mentioned in my first post, there is an inconsistency with the pin for Row/Column 30. Given how the IC is configured for 8 x 32 output, it's the pin for Column 30. More testing for frequency of output between VDD and row/column pins reveals that this pin has 0.000Hz, while all others are 2.4kHz. Further, while resistance through the chip between VLCD and all other row and column pins is ~ 350kOhm, for the Column 30 pin it is 500MOhm to OL. These signs do not look right and suggest that all is not well inside this chip. 

I'll be looking for a replacement. A dude in the UK is selling singles on eBay for ~ 28 Pounds. Or I can buy a minimum quantity of 17 from Hong Kong, for about the same price.

Any suggestions for where I might find one at a reasonable price? Mouser, Element14 and RS-Online are no go, from what I can see.

Thanks. Soldering in a new 64 pin chip will be fun!

[cantata.tech]

This might be a bodgy way, I know, but if it is just one function of the IC that is blown, consider doing just a repair to that function.

Sometimes these IC's are made bigger so they actually look like they are complex and doing a lot of stuff. And are just filled with "air" to fool people.

Yes, you can desolder and replace the entire IC, that's the right way to do it.

If you are "busy" maybe you could just do a breadboard of the damaged part of the IC and solder that on for now.

Until the new IC's arrive from where-ever.

[pej]

I have exactly the same fault on a CDR-23 - LCD suddenly stopped working but everything else ok.

CDR 23 does not have a detachable face plate, but uses very similar ICs - NEC 1299 662 and PCF 8578.

Did you ever manage to fix this?  Replacing the PCF 8578 is certainly not easy.
Thanks.

[Valden]

Hi Pej.

No, I haven’t finished this project yet, but I am satisfied that I’m on the right track; that the PCF 8578 should be replaced. I tested a working faceplate in my radio and it was good, and vice versa, my faceplate was lit up but with no characters in the other radio.

I practiced desoldering a 64 pin IC of the same size from a board scavenged from a dead machine. I used a hot air nozzle with my Ersa station and struggled to get enough heat in. I asked my wife to help with a Dewalt hot air gun, to provide background heat. This worked, but it wasn’t tidy. I’m looking into getting an IR preheat table - more controllable - though the double sided nature of the Becker board could be a complication. Clues welcomed. I also need to rig up a suction cup and spring setup, to lift the chip off the board once all those 64 legs are hot enough. Again, clues are welcome.

It’s good that you’ve made contact. If I do have to buy a bulk quantity of these chips I’ll share one with you. Or have you found a source for singles at a sensible price?

Regards, Valden.

[Jeff eelcr]

Although Becker has changed ownership and no longer sells parts or manuals they do still repair most of their equipment.
The removeable faceplate is a part and the chassis is another part both can be repaired seperatly.
Jeff 

[Valden]

Hi Jeff.

I’ve become quite expert at disassembling the removable faceplate and could fix it in five minutes, with a replacement circuit board. I’ll wager that’s how Becker’s repair people do the job. Or am I wrong? Do they undertake board level component repairs, such as I need to do? Any idea?

Do you know which countries their repair service is available in? I’m in Australia.

Thanks. Valden.

[Jeff eelcr]

For many years we repaired Becker units, we were in process to become a warrenty station.
All that went away as soon as Harmon got involved. I do not remember that model type.
Their repair center in the U.S. is all I ever delt with they repaired to the component most times
but would do exchanges on some damaged units, and we could do advanced exchange with them.
Most were Mercedies units 600 series and 700 series units we rebuilt/repaired/exchanged as needed.
As long as it is a removeable face type unit it should be repairable by itself (do not need chassis)
with it so shipping would be less if it must go to another country.
Jeff   

[Valden]

Thanks Jeff.
That’s a useful repair service, which I will keep in mind.
Regards, Valden.

[Valden]

Progress: I’ve removed the Philips PCF 8578H LCD driver chip using hot air.  No damage done. The vacant chip area was then cleaned with fluxed solder wick and an iron. Then IPA with cotton buds to clean the residue. Pic attached. Probing shows that all of the contact pads and associated throughs and traces are in good shape.

With this completed I’ll order some NXP PCF 8578H ICs I’ve found in Hong Kong for around $8 USD. I should have a couple spare so get in touch if you need one to do the same repair. Perhaps wait for my success or otherwise first. 🙂

[Valden]

Hello all.

It's fixed! Pics attached.

I sourced a couple of NXP PCF8578H LCD driver chips from sicstock.com in China. These were $8.13USD each, plus $7 postage. They arrived by post to Australia in a couple of weeks.

Today I installed a new PCF8578H chip onto the Becker face plate circuit board. I used a drag solder technique, using a 1.6mm wide tip with a solder well. Only the smallest amount of solder was needed, with a minimum of liquid flux applied to the pads and the chip's legs.

After soldering I checked the chip's pins with a 35mm moderate wide angle lens from an old film camera. I found a few bridges so fluxed and dragged again to remove most. I used solder wick and flux to remove a couple of stubborn ones. I cleaned the chip and pins with isopropyl alcohol and cotton buds. Then I checked all of the pins for connectivity to the respective pads and circuit traces, as well as for any remaining bridges between pins. I found one bridge which wasn't obvious and wicked this away. Another check for connectivity and bridges - it all seemed good. I reassembled the board into the face plate, making sure the flexible contact strip was clean and the board's ground was electrically connected to the metal LCD frame.

As I walked out to the car I kept saying to myself that it probably wasn't going to work. After snapping the faceplate into position in the radio and rotating it up to its closed position I pressed the On button without pausing to remember what it should look like. In a second I saw the display showing the startup sequence and then the channel and button legend. It's working perfectly. Wow! I wish I'd had a camera on my face.

Anyway, if the LCD display in the removable faceplate of your Becker CDR-220 CD Radio (or similar) stops working, the problem could be the PCF8578H LCD driver chip. As mentioned earlier, probing of this chip revealed that one of the column display output pins was reading OL for resistance and 0 for frequency when the board was powered. All of the other row and column display pins provided consistent and sensible resistance and frequency readouts. Only 1 of the 64 pins was misbehaving.

If someone in Australia has the same problem I have a spare PCF8578 chip which I could post to you. I'll be happy to compare your diagnosis with mine, beforehand.

Regards, Valden.

[pej]

Valden
This is fantastic news to see you have this working and thank you so much for sharing.

My apologies for not responding earlier.  Yes there is an alternative way of removing these components with low melting point solder which I have not tried yet.  You can see it used here:
https://hackaday.com/2021/06/02/make-your-desoldering-easier-by-minding-your-own-bismuth/
It made me wince a little watching it done, but it is very much lower heat that should not damage things.

My CDR23 seems similar to CD220 in many ways except the face-plate is not removable on CDR23.  Neither is there easy access to the PCF8578H with a scope unless an extender ribbon cable cable is made to connect the front panel PCB to the main unit.  I sadly cheated, took a risk, and purchased a new front panel PCB. That fixed it.

I will guess, with exactly the same fault symptoms, mine may well also be the PCF8578H.  Until now I have had no plans to remove  the PCF8578H but having seen this news I might just get curious enough to try the above desoldering and see if a replacement chip works.

Thanks again and well done.
Peter

[Jeff eelcr]

Nice work, looks great.
Jeff

[Valden]

Hi Peter.

Yep, I’m still smiling from getting this repair done, at the board level.

I saw your thought about using low melting point solder. It could be a good idea as it’s a fairly low impact approach to removing a component, though possibly a bit messy. I decided to use hot air for two reasons: I wanted to keep the board as clean as possible, and I wasn’t concerned about heat damage to the IC I was removing.

I used a DeWalt hot air gun to provide background heat of around 100°C on the board, then used hot air from my workstation to heat the chip’s legs. I had the board resting over a Pyrex jug and it slipped. In setting it straight I had the hot air too close and the IC made a pop noise. Just as well I didn’t need it again. Being clumsy with hot air can be damaging! But it soon loosened and I copied Dave’s method of using Blue Tack on a spudger to lift it off. For the future I want an IR heat pad, with a board clamp over it, a shroud for the chip and a vacuum lifter. That would make life easier. However, my make-do method worked.

If you do find yourself soldering a new PCF8578H onto your board, use the barest minimum of solder for dragging over the pins. Cleaning up the bridges from excess solder was the main challenge I had.

Good luck.

Regards, Valden.

[pej]

Valden
Thanks for these great tips.  Yes, agreed, the low melting point solder may cause bridging issues.  Your method has produced excellent results and wouldn't even know it had been changed looking at the photos you kindly provided.

I did not quite realize the PCF8578H is discontinued.  But they are still on sicstock.com which is great thanks. I would never of found it.

The blue tack tip is excellent too at gently lifting.

If at some point I do go ahead, I will post on here any useful results for my particular radio variant which shares many of the same components.
Thanks again for all your advice
Peter