Seaward PAT 2000I - UK Vintage Radio Repair and Restoration Discussion Forum

Alistair D · 2nd Nov 2016, 1:21 pm

I have just repaired a Seaward PAT 2000I I was given a year or so ago. The problem was that most of the keypad was dead. That was caused by a faulty 4053 chip connected to the keypad matrix.

The problem I am left with is that if I power the tester up in less than 5 minutes after a power down it will often come up with the message "VOLTS ON NEUTRAL! PRESS # ONLY IF SAFE" Pressing the # key clears the message and then everything works fine. According to the manual this should only happen if there is greater than 50V between N and E. I am happy that this is not the case on any of the sockets I have tried it on.

Does anyone else use one of these testers? Does it exhibit the same characteristic or do I have another fault?

Al

McMurdo · 2nd Nov 2016, 1:54 pm

Sounds like a fault. I used to service PAT testers occasionally and this model was a regular visitor, I think they were also badged as 'RS'. I've never seen that message AFAIK. They used to fill me with dread.

Alistair D · 8th Nov 2016, 4:12 pm

Definitely a fault. I am now at the point of giving up on it. What I have found is that the problem is being caused by the 4052 I replaced before. Basically the volts on neutral analogue signal, at quite a high impedance, is passed through one of 4052's channels.The 4052 itself is adding between -200 and -300mV to the signal. When the signal reaches 300 mV the error is flagged. The supplies are pretty stable at plus and -4.9V and manually opening the channel by shorting the S0 line to ground returns both the input and output to 0V so it seems to be the chip itself that is responsible. Unfortunately the chip is a surface mount part so not easy to swap.

Any ideas before I end up wrecking the tracks trying to replace the chip again?

Al

McMurdo · 8th Nov 2016, 5:27 pm

At least you've narrowed it down, shame to give up after your hard work! It's got to be worth a new chip. Where was the other one from, a reputable source? Was it the same manufacturer?

Herald1360 · 8th Nov 2016, 7:52 pm

Quote:

Originally Posted by Alistair D

Unfortunately the chip is a surface mount part so not easy to swap.

Any ideas before I end up wrecking the tracks trying to replace the chip again?

Cut the legs on the chip with a scalpel or fine nosed cutters then remove the legs gently individually. They should stick to the iron bit if gently slid away from any track approaching the pad. Clean the pads up carefully with fine solder wick. Spot down a couple of corner legs then work round the rest.

Sorry if this is a granny egg suggestion.....

TonyDuell · 8th Nov 2016, 7:56 pm

Does the replacement have to be surface mount? Is there enough space to wire up a (turned pin) DIL socket and then plug in a DIP device? That would make it easier to replace or to select one that will work.

SiriusHardware · 8th Nov 2016, 9:58 pm

Alternative removal approach:-

Flood all the pins down each side together with solder - (lead / tin solder), effectively making the device into a 2-pin device. Then, use two soldering irons (one in each hand, not like chopsticks!) to melt the solder on both sides at the same time and 'tweezer' (or flip) the IC off the board.

Flooding the pins has the advantage that it forces all the pins and pads to be at roughly the same temperature, so you are less likely to overheat a single isolated pin and burn its unconnected pad off the PCB.

Wick off the excess solder, fit the new IC.

2nd Nov 2016, 1:21 pm	#1
Alistair D Nonode Join Date: Jan 2010 Location: Edinburgh, UK. Posts: 2,008	Seaward PAT 2000I I have just repaired a Seaward PAT 2000I I was given a year or so ago. The problem was that most of the keypad was dead. That was caused by a faulty 4053 chip connected to the keypad matrix. The problem I am left with is that if I power the tester up in less than 5 minutes after a power down it will often come up with the message "VOLTS ON NEUTRAL! PRESS # ONLY IF SAFE" Pressing the # key clears the message and then everything works fine. According to the manual this should only happen if there is greater than 50V between N and E. I am happy that this is not the case on any of the sockets I have tried it on. Does anyone else use one of these testers? Does it exhibit the same characteristic or do I have another fault? Al __________________ I won't tell you how I discovered that.

2nd Nov 2016, 1:54 pm	#2
McMurdo Dekatron Join Date: Jun 2009 Location: Staffordshire Moorlands, UK. Posts: 5,274	Re: Seaward PAT 2000I Sounds like a fault. I used to service PAT testers occasionally and this model was a regular visitor, I think they were also badged as 'RS'. I've never seen that message AFAIK. They used to fill me with dread. __________________ Kevin

8th Nov 2016, 4:12 pm	#3
Alistair D Nonode Join Date: Jan 2010 Location: Edinburgh, UK. Posts: 2,008	Re: Seaward PAT 2000I Definitely a fault. I am now at the point of giving up on it. What I have found is that the problem is being caused by the 4052 I replaced before. Basically the volts on neutral analogue signal, at quite a high impedance, is passed through one of 4052's channels.The 4052 itself is adding between -200 and -300mV to the signal. When the signal reaches 300 mV the error is flagged. The supplies are pretty stable at plus and -4.9V and manually opening the channel by shorting the S0 line to ground returns both the input and output to 0V so it seems to be the chip itself that is responsible. Unfortunately the chip is a surface mount part so not easy to swap. Any ideas before I end up wrecking the tracks trying to replace the chip again? Al __________________ I won't tell you how I discovered that.

8th Nov 2016, 5:27 pm	#4
McMurdo Dekatron Join Date: Jun 2009 Location: Staffordshire Moorlands, UK. Posts: 5,274	Re: Seaward PAT 2000I At least you've narrowed it down, shame to give up after your hard work! It's got to be worth a new chip. Where was the other one from, a reputable source? Was it the same manufacturer? __________________ Kevin

8th Nov 2016, 7:56 pm	#6
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,224	Re: Seaward PAT 2000I Does the replacement have to be surface mount? Is there enough space to wire up a (turned pin) DIL socket and then plug in a DIP device? That would make it easier to replace or to select one that will work.

8th Nov 2016, 9:58 pm	#7
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,586	Re: Seaward PAT 2000I Alternative removal approach:- Flood all the pins down each side together with solder - (lead / tin solder), effectively making the device into a 2-pin device. Then, use two soldering irons (one in each hand, not like chopsticks!) to melt the solder on both sides at the same time and 'tweezer' (or flip) the IC off the board. Flooding the pins has the advantage that it forces all the pins and pads to be at roughly the same temperature, so you are less likely to overheat a single isolated pin and burn its unconnected pad off the PCB. Wick off the excess solder, fit the new IC.