Mastervolt Combi refurb

[nicknorman]

Our Mastervolt Combi 12v/2500w/100A is 12 years old now, and the on/off/charger rocker switch has started playing up. I have taken it home to fix the switch but I also plan to replace the electrolytic capacitors since they seem to have a limited life and dry out/lose their value which can cause other bits to fail catastrophically. A stitch in time...

Just wondering if anyone else has done this, and any tips...

[jonesthenuke]

We have the same unit of much the same age. I would be very interested to see how you get on.

[dmr]

I don't know. I have seen failed electrolytics but that's in really old (vintage) equipment. 12 years is just not that old so unless its bad design (too much ripple current?) I would be surprised if its worth it. Electrolytics are not usually that critical as long as they work. 

You can solder well so probably have nothing to lose as long as the new ones are good and not dodgy chinese stuff, though desolderring multi-layer boards always carries a bit of risk.

Mr Cox did a precautionary overhaul of our Travelpower a couple of years ago and I think he said its the big resistors rather than the caps that go. I take the advice of an experienced  hands on repair man seriously, experience often beats theory 😀

Any big hot running power transistors are also high risk components.

 

There are capacitor kits available for some old audio equipment but this might be just "silly HiFi" stuff.

 

I just cleaned all the fluff and dog hair out of my 100amp alternator and the next day it melted its windings so I obviously know nuffin about electricity 😀

[nicknorman]

19 minutes ago, dmr said:

I don't know. I have seen failed electrolytics but that's in really old (vintage) equipment. 12 years is just not that old so unless its bad design (too much ripple current?) I would be surprised if its worth it. Electrolytics are not usually that critical as long as they work. 

You can solder well so probably have nothing to lose as long as the new ones are good and not dodgy chinese stuff, though desolderring multi-layer boards always carries a bit of risk.

Mr Cox did a precautionary overhaul of our Travelpower a couple of years ago and I think he said its the big resistors rather than the caps that go. I take the advice of an experienced  hands on repair man seriously, experience often beats theory 😀

Any big hot running power transistors are also high risk components.

 

There are capacitor kits available for some old audio equipment but this might be just "silly HiFi" stuff.

 

I just cleaned all the fluff and dog hair out of my 100amp alternator and the next day it melted its windings so I obviously know nuffin about electricity 😀

Interesting. 12 years old but it has been on pretty much 24/7/365 for 12 years. That is over 105,000 hours. Which is more than the quoted life from a lot of manufacturers, but of course it depends a lot on the temperature and most of the time that will have been low.  I think the electrolytics will be showing signs of sickness if they need replacing (bulging ends). I'll have a look, anyway.

I know Sky boxes were renowned for having dodgy electrolytics and you could get repair kits.

Anyway, failures have causes and perhaps Mr Cox's resistors failed because some electrolytics had severely reduced capacitance due to old age. Who knows?

[dmr]

3 minutes ago, nicknorman said:

Interesting. 12 years old but it has been on pretty much 24/7/365 for 12 years. That is over 105,000 hours. Which is more than the quoted life from a lot of manufacturers, but of course it depends a lot on the temperature and most of the time that will have been low.  I think the electrolytics will be showing signs of sickness if they need replacing (bulging ends). I'll have a look, anyway.

I know Sky boxes were renowned for having dodgy electrolytics and you could get repair kits.

Anyway, failures have causes and perhaps Mr Cox's resistors failed because some electrolytics had severely reduced capacitance due to old age. Who knows?

Put like that it does sound rather a lot.  I think most older electronic failures are stress (or strain) due to cyclic thermal expansion which is why power resistors and transistors fail, plus odd semiconductor things.

I remember taking a load of huge electolytics out of some vintage equipment and it was great fun to connect them backwards accross a bench power supply. They hiss for a few seconds giving you time to run away before they go bang.

 

If they are easy to get out then replace them, or at least the bigger ones.

[Jen-in-Wellies]

10 hours ago, dmr said:

Put like that it does sound rather a lot.  I think most older electronic failures are stress (or strain) due to cyclic thermal expansion which is why power resistors and transistors fail, plus odd semiconductor things.

Yes, thermal expansion/contraction induced fatigue of solder joints is a principal cause of failure. Can be mitigated in design to some extent, but not eliminated. In use, keeping stuff powered up at a constant power level in a stable temperature environment is best. One of the worst ones used to be old style CRT televisions. Their design had to be based on the assumption they would be turned on and off  up to six times a day for ten years and they ran hot when on. Then there are lifespans of individual components, like electrolytic capacitors.

[Tracy D'arth]

This total replacing of capacitors is an audiophool fad. It is no substitute for proper faultfinding.

[IanD]

15 hours ago, nicknorman said:

Our Mastervolt Combi 12v/2500w/100A is 12 years old now, and the on/off/charger rocker switch has started playing up. I have taken it home to fix the switch but I also plan to replace the electrolytic capacitors since they seem to have a limited life and dry out/lose their value which can cause other bits to fail catastrophically. A stitch in time...

Just wondering if anyone else has done this, and any tips...

Electrolytics do deteriorate with age, faster at higher temperatures. There was also a period around then when there were a lot of electrolytic caps around which failed prematurely (usually showed up as bulging ends) which lead to many equipment failures, including Sky boxes and lots of other gear, both cheap and expensive -- the manufacturers changed their recipes and this went away.

 

If your Mastervolt doesn't have this problem and generally doesn't run hot then it's probably not worth the hassle and cost of replacing the electrolytics -- if you do, focus on ripple rating as well as voltage/capacitance. But if you don't mind all this, it will give you more peace of mind... 🙂

Edited November 5, 2023 by IanD

[Sea Dog]

54 minutes ago, Tracy D'arth said:

It is no substitute for proper faultfinding.

However, in the case of Mastervolt, any faultfinding is severely hampered by an absence of information and outright denial of technical support (in my experience at least). Under those circumstances, a willy-nilly component change is perhaps not as willy-nilly an approach as it might otherwise be.

My identical (defective) Mastervolt Combi unit is sitting in my garage at home awaiting inspiration or for me to get over the idea of simply throwing it away.

[Tracy D'arth]

There are repairers, for a price. They will buy duff units too, better than the recycling bin.

[Mike55]

On 04/11/2023 at 22:04, nicknorman said:

Our Mastervolt Combi 12v/2500w/100A is 12 years old now, and the on/off/charger rocker switch has started playing up. I have taken it home to fix the switch but I also plan to replace the electrolytic capacitors since they seem to have a limited life and dry out/lose their value which can cause other bits to fail catastrophically. A stitch in time...

Just wondering if anyone else has done this, and any tips...

I too have the same unit and have had problems with the on/off/charger rocker switch especially in the charger position. I sprayed around the switch with contact cleaner (after a suggestion on this forum) and that got the switch working again. I've also found that rocking the switch back towards off slightly seems to help. I try and avoid operating the switch once I've got it working. I decided this was lower risk (& less work) than taking the thing to pieces to replace the switch.

I'd be interested to know how you get on particularly with the switch.

[nicknorman]

In the end, since I could see absolutely no sign of distress from the Electrolytics, and having convinced myself that although it had been powered up for 12 years, most of that time it was cool with virtually no ripple current (etc etc)... and not to mention that it all looked a bit complicated, I decided to leave well alone and just separated the boards, wiped out all the dirt with a damp cloth (anti-static) and replaced the offending rocker switch. If anyone is interested the rocker switch is RS item no. 741.0886. Well, that is more or less the identical switch but with PCB pins rather than fat spade terminals. But since there are flying wires soldered onto it, that doesn't matter.

Put it all back together and it still works! Phew!

34 minutes ago, Mike55 said:

I too have the same unit and have had problems with the on/off/charger rocker switch especially in the charger position. I sprayed around the switch with contact cleaner (after a suggestion on this forum) and that got the switch working again. I've also found that rocking the switch back towards off slightly seems to help. I try and avoid operating the switch once I've got it working. I decided this was lower risk (& less work) than taking the thing to pieces to replace the switch.

I'd be interested to know how you get on particularly with the switch.

Replacing the switch was pretty easy, partially undo the 2 screws at the bottom to slide off the connection bay cover before you start.

Then undo the front cover (2 screws each top and bottom) and carefully lift off as there is a ribbon cable connecting to the logic pcb. Carefully pull off the ribbon cable connector from the pcb, then the front plate can be moved to a bench. Undo 3 screws holding the green plastic thing on (two on front side, one on rear side which is longer and a self-tapper). Unsolder the 3 black wires that go to the switch. It might be possible to push the switch out with the little PCB in situ but it is just held in with plastic clips - one to push back slightly, then it pops off. That allowed the old switch to be pushed out and the new one pushed in. Replace pcb so 3 clips are engaged, re-solder the 3 black wires and reverse the disassembly.

 

RS part no. 741-0886, £3.66. Unfortunately RS have a handling charge for small orders these days. Shame I didn't know you needed one as I could easily have ordered 2. Too late now!

 

You might find the switch elsewhere, it is Marquardt SPDT On-Off-On, manufacturer's part number 1808.2102.

Bad design really, it has silver plated contacts. For logic switching such as it's used for (ultra low current) they should have used gold plated. Never mind, I suppose it lasted 12 years!

Edited November 7, 2023 by nicknorman

[Mike55]

Did you have to remove the unit or could you replace the switch with it still on the wall?

[nicknorman]

14 minutes ago, Mike55 said:

Did you have to remove the unit or could you replace the switch with it still on the wall?

 

I did remove it and take it home, but you could replace the switch with the unit still on the wall, provided you can access the screws that point up and down (ie there is enough clearance from floor/shelf and ceiling to get a screwdriver in). I would want to ensure the thing was fully powered down, ie 12v fuse removed and then switched on to deplete the large capacitors and then maybe left for a bit to ensure there is nothing at high voltage. And obviously not connected to shore power!

 

When you reconnect the 12v there will be an almighty flash as the input capacitors charge up again. This will scare the whatists out of you. So it is better to use a resistor of say 50ohms or thereabout, to put in place of the fuse for a few seconds, to charge the caps up slowly. Then quickly swap to the fuse before the caps can discharge.

 

Oh I forgot to mention, partially undo the 2 screws at the bottom to slide off the connection bay cover before you start.

Edited November 7, 2023 by nicknorman

[Mike55]

OK, thanks for the tips. Mine has a fair bit of space around it and the charger has a 12V isolator (as well as an enormous bolted 250A fuse) so any flash would be within the isolator so perhaps not quite as scary as replacing the fuse.

 

I want to get the replacement switch before I start the job. 

Edited November 7, 2023 by Mike55

[nicknorman]

7 minutes ago, Mike55 said:

OK, thanks for the tips. Mine has a fair bit of space around it and the charger has a 12V isolator (as well as an enormous bolted 250A fuse) so any flash would be within the isolator so perhaps not quite as scary as replacing the fuse.

 

I want to get the replacement switch before I start the job. In the post above you mention the original has spade terminals. I've identified the spade terminal equivalent to the switch you used: Marquardt 1808.1102, but unfortunately RS don't stock it, so I'll need to go elsewhere.

There is no need to worry about the type of terminal since the switch has short flying wires between it and the board, soldered on. It makes no difference if you solder on to the spade terminal version, or the pcb mount version. In fact the latter is slightly better as it presents less heat sink.