XPR7550e Home/Back key not working

[tropiradio]

So got this radio and everything seemed to work fine, except the Home/Back key on the KB does nothing. I assumed it would be a defective switch even though that key has a reassuring click feel as all others, but somehow the contacts where not working. So replaced the keyboard PCB and also the flex between the main radio board and the keyboard PCB, but that did not solve the issue.

At some point was able to get another XPR7550e radio and exchanged the main board and chassis, and the fault followed the main board. In other words, the keypad that had the non working Home key started working fine when attached to the other radio, and the good keypad when attached to my radio also had the same problem with the home key. So the fault seems to be on the main board.

Before I send this radio back, which will be a huge pain in the posterior, first because it is needed, and secondly I am not in the US and my only options are very expensive DHL or Fedex shipments which I anticipate might run about $100, does anyone have any suggestions about this problem with the Home key, or seen it before?

Worth mentioning I programmed the original codeplug back into the radio, and that did not make any difference. I know there is no such thing as any codeplug parameter affecting just the Home/Back key, but did it anyway just to rule it out.

The radio has R02.21 firmware, so hello v2 CPS

Any comments appreciated.

 

[waynedc]

Did you set your home channel and zone in the CPS?

 

[tropiradio]

Yes of course zone and channels are programmed. But I am talking about the Home/Back button on the keypad, the one being used for the menus so you can navigate/backstep out of them and the different options, or if kept pressed for 2 seconds will take you back to the main/home screen.

 

[waynedc]

That is the setting I asked about - you need to set the home channel and the associated home zone in the CPS for the home button to work.

 

[K2NEC]

Before you do anything, put the radio into service mode and verify that the button functions. If it's not recognized by the radio when you press it, there's a problem.

 

[tropiradio]

I tried left arrow 3 times and right arrow 3 times to get into service mode, but it does not work. I have another 7550e and on that radio it responds by going into the RSSI screen. Then when I press the home button it goes back to regular channel screen. I seem to remember there is a CPS setting checkbox to enable service mode, Let me verify the status on the radio with the problem and report back.

 

[tropiradio]

Just looked into the codeplug and Test Mode is enabled (checked).

I wonder if the radio not responding to the side arrows to get into test mode has to do with the keyboard problem.

Just went into the message compose window and it is now apparent that several other keys do not seem to be working. The right arrow does not respond (but left, up, down respond ok), the 3, 6, 9, and space/# key do nothing, but the */< (back) works. Also the 7, 8 and 9 keys are non functional as well, but 1, 4, 2 and 5 keys do work. The non-working keys would not even cause the display backlight to come on.

 

[K2NEC]

I tried left arrow 3 times and right arrow 3 times to get into service mode, but it does not work. I have another 7550e and on that radio it responds by going into the RSSI screen. Then when I press the home button it goes back to regular channel screen. I seem to remember there is a CPS setting checkbox to enable service mode, Let me verify the status on the radio with the problem and report back.

That's not how you put it into service mode

 

[tropiradio]

That's not how you put it into service mode

Correct, I meant to say Test mode. What is again the side button combination on power up for this radio to go into service mode? I rarely use it so keep forgetting.

 

[tropiradio]

OK side button 5 times after selftest tone, then advanced all the way to the Button/Knob/PTT Test Mode, and the following keys do not give the proper expected results (no reaction at all):

right arrow, home, 7, 8, 3, 6, 9, and #

All other keys, the side and top buttons, PTT and both controls do get the correct response.
Looks like a row or a column connection to the host processor is bad.

 

[K2NEC]

There's your answer then. Now to figure out if it's a board issue or a flex issue.

 

[tropiradio]

So dug into the detailed SM, and found the keyboard connections from the keypad. Unfortunately no PCB or schematic of the keypad board itself in the manual, so not easy to determine which keys belong to what row and column and determine which connection might be faulty. But at least its a start to pinpoint those row and column connections on the connectors. BTW some rows and columns are present on two connectors, most are on J4100, but there are also some redundant ones on J4200. See attached JPG.

From those conectors is goes straight to U1000, so there is a possibility that one of those solder balls under the chip might not be making proper contact and might need reballing, something I am not comfortable doing. In any event will check all the external connections with a magnifier to see if I can spot something amiss out there.

Anybody have the page of the service manual that shows the actual schematic of the keypad board and switches? I am using MN002182A01-AA from 2016.

 

[tropiradio]

There's your answer then. Now to figure out if it's a board issue or a flex issue.

Fault has to be on the main board, if I change the whole radio front and boards into the mainboard of another 7550e the keypad starts working fine. Also I had previously replaced both the keypad board and flex, so both are ruled out.

I'm thinking there are several possibilities on the main board: a faulty contact on one of the connectors J4100 and J4200, a faulty trace between the connector and U1000 processor, or a balling problem under U1000.

Looking very closely at the connectors and surrounding parts with a 10x magnifier but cannot spot any defect.
Last thing, I think unlikely, that one of the row/col bypass caps is shorted to ground, but not sure if that would not cause the whole keypad to stop responding, like with a stuck key. Guessing it will not hurt to check those line for any ground short.

Also wanted to check continuity from the other end of the keyboard flex to J4100, but with the connector in place J4100 is completely covered up and inaccessible.

Any other ideas?

 

[K2NEC]

Where did you get the radio and how long have you had it?

 

[tropiradio]

Where did you get the radio and how long have you had it?

Purchased a couple of weeks ago from Cape Ltd as new surplus with antenna only. Afterwards they even sent me a keypad board and flex for free to try and get it fixed on my end, but that did not solve the issue. So they said to return the radio and they will send me another new one. Since they had already authorized me to open it up, just wanted to give it one last shot to see if it might be something relatively simple that I could fix here myself and avoid having to pay expensive Fedex/DHL charges to get it back to Miami.

Been dealing with Cape for years for mutichargers and radios, always happy customer, good prices, and very rarely had a problem and they always have stood behind their sales. Sounds like I will have to bite the bullet this time and send it back, I really want the radio to be fully operational. Bought it as my personal UHF radio and eventually also for customer demo of digital features, and mainly because of a new Moto repeater project to be installed next week, so really needed it and other than the keyboard problem it works perfectly.

 

[K2NEC]

At least you have a seller that stands behind their products and service. If you can't fix it, send it back.

 

[merlin]

If you know the keypad flex to be good, I bet a cold/broken solder connection at the flex connector.
There is a right and wrong way to seat the ribbon in the connector and the catch should lock on both ends.
A bad solder connection means some SMT rework, and that takes advanced tech background.
Sounds like you are on top of things if you have a scope, start probing the suspect connections and traces.

 

[tropiradio]

If you know the keypad flex to be good, I bet a cold/broken solder connection at the flex connector.
There is a right and wrong way to seat the ribbon in the connector and the catch should lock on both ends.
A bad solder connection means some SMT rework, and that takes advanced tech background.
Sounds like you are on top of things if you have a scope, start probing the suspect connections and traces.

I figured something like that might be the problem, but I closely inspected the mating connector for J4100 and J4200 both involved in the keypad rows and columns, and both flex are positively seated correctly and locked. Visually could not find anything wrong on any of the connector pins or solder joints, wanted to test continuity between the end of the keyboard flex and the soldered pins of J4100, but once that flex connector is locked in place over it it completely covers up the connector and the solder joints so it is impossible to access them even at the bypass caps.

Since the front of the radio works perfectly on the other chassis/main board, the problem has to be either on those connectors or the traces between them and the processor which are a straight through connection except for the line bypass caps. Worst case scenario one of the ball solder joints under the processor U1000 itself is faulty. I do have a hot air station and experience with SMD work, but reballing is beyond with what I would be comfortable doing, so the radio will have to be sent back for replacement. And while I have to return it, will also try to get a replacement radio with earlier firmware so I can use CPS16, although I am not going to hold my breath on that.

Thanks for the input so far guys, much appreciated.

 

[tropiradio]

At least you have a seller that stands behind their products and service. If you can't fix it, send it back.

Yes, at least something positive.

BTW do you (or anybody) know which firmware release started to require CPS V2 on the 7550e? My other 7550e VHF is R02.09 and works with CPS16, this one UHF is R02.21 and obviously requires cps V2. I am wondering if R02.20 or R02.19 would still work with CPS 16, or was the R02.09 the last one?

 

[K2NEC]

Yes, at least something positive.

BTW do you (or anybody) know which firmware release started to require CPS V2 on the 7550e? My other 7550e VHF is R02.09 and works with CPS16, this one UHF is R02.21 and obviously requires cps V2. I am wondering if R02.20 or R02.19 would still work with CPS 16, or was the R02.09 the last one?

2.09 was the last one. 2.10 was the start of CPS2.0