Ribbitt 1985 PT-40 repair thread

[Vonhitch]

Ok so I thought I would start a repair thread on all things pertaining to my 85 PT-40 that I fix. Put it all in order in one place so I can refer back to it and maybe others in the future will find it helpful. Ill post part numbers and links for parts where I can. Im not the most articulate or internet savvy person but Ill try.

So start with todays work. Ive been replacing all the capacitors on the two boards in my PMMI musical horn. When I bought the bus I only had one channel working and it was super faint you had to basically put your ear to the horn to hear it. So I started sourcing the Caps off the net and well ended up with getting my second channel back on the board with the Chips or Proms I guess they are called? But it was still no volume a little better but not really. So then I went after the smaller board with the amps on it replaced all of those Caps except the big 1000 UF caps see pic #1. Still no change. Today those big caps showed up so I soldered those in and BOOM it plays like a champ!! Now here is my question. When I press the power switch Pic #2 it plays the desired song to completion. But when I press the “play” button on the dash Pic#3 shouldnt it play the song again? I have to power it of and on again to play it. That doesnt make sense to me. So I tested the switch it has continuity through it so that works. I then chased the wires from that switch through the ribbon cord to the board they 2 of them are on the right of the connector Pic #4 then on the Board those to some big holes that have nothing soldered in them and on the board they go nowhere. That seems totally odd to me. The only thing I can think of os the box was changed at some point. Help me here how do your music horns function on the dash switches?
Thanks Dave

[Fullerr]

Nice work. My musical horn is self contained and mounted on my dash. I do not have remote dash switches. After selecting a song and it plays through, pressing the play button will repeat the song.

[Vonhitch]

Ok where I said in the above post that the ribbon cable went through the plug to nothing…. Yea disregard that I was on the dang wrong pin I chased it with continuity tester through the board to a resistor and its solder job wasnt good just touched that and now the “play” switch works today was good now its a BIRD again.
Dave

[DirtDigger]

One of those skills I am still learning - soldering those tiny wires and understanding the circuitry. Glad you were able to get it working.

[Vonhitch]

Middle cruiseair wasnt working. The guy I bought it from had put new stainless screws in the outside grills at the unit before I bought it. Welp he used 2” screws put one right through the line. He said he would fix it before I picked it up. Welp he “Fixed” it with regular old propress fittings. Yes they do make AC ones and special jaws but thats not what was used. Anyways a Friend is a commercial AC guy we cut that BS out brazed in a bit of new line and put a 110 lbs of nitrogen in it. Plan is to leave that see how it does before we vac and charge it. The front unit flashes for a bit and a bit low per the gauge which is prob why it iced over in florida that will get charged when we do the middle unit charge. Now the rear unit only flashes for a couple mins then runs solid. That unit puts out ice cold air about 20 degrees split RA to SA. The prob with getting gauges on that one is the valve is stuck. Moral of the story dont use pro press on AC !!
Plan to charge this next week if it holds
Dave

[CrashTestDummy]

Nice splice job! Yeah, when I'm working on things in our bus (or other vehicles, too), I occasionally come across a screw/bolt that's obviously a replacement and they used whatever they had to replace the one they lost.

The first thought is 'W-T-H', then, what did they puncture/pinch/break behind that? You always have to be cognizant of what's behind that panel/brace/etc., because there's literally 10# of 'stuff' packed into these 5# boxes we call a Wanderlodge!

[Vonhitch]

Originally Posted by CrashTestDummy

Nice splice job! Yeah, when I'm working on things in our bus (or other vehicles, too), I occasionally come across a screw/bolt that's obviously a replacement and they used whatever they had to replace the one they lost.

The first thought is 'W-T-H', then, what did they puncture/pinch/break behind that? You always have to be cognizant of what's behind that panel/brace/etc., because there's literally 10# of 'stuff' packed into these 5# boxes we call a Wanderlodge!

Yup the fact is too dont use pointed screws use a blunt one !!! That splice BTW is the domestic water type Pro Press fitting with the rubber O rings the tell apparently is the water ones leave a hex shaped crimp. The hvac ones dont leave a hex shape. This is all new to me we brazed it its not pretty its all black n ****** looking but I bet it holds compared to this “easy way out fix”
Your 100% on paying attention to the size and length of screws
I attached a pic of the pro press we cut out.
Dave

[Vonhitch]

Started to figure out why my tank sensors didnt work. Well the propane did but the other three tanks all showed empty not full. Took the panel down and noticed the small 5v voltage regulator on the clock was burning the board. See pic #1 it also was over 200 degrees. Im fixing tonight I will share that in few minutes when im done.

So back to the holding tank sensors and board. Pic #2 shows that the black, grey and fresh water sensors all combine behind the panel.thats green, red, yellow and brown in the pic. I noticed on other posts people stated that blue wires at the tank sensor (the ones that daisy chain) were the negative side. Thats not the case on my panel. On my panel except the propane all the tank sensors get 12v from the board. The blue wires arent ground they are power back to the board. Each sensor as it adds resistance triggers another light. Mine being all dead I knew it wasnt the sensors and when sensors are dirty they trigger more of a false full reading. So I probed around my panel jumped the sensors ect. Not much to see. So i determined the panelwas sending power out and back but it wasnt going through the board. Turns out the pin connector at the board simply had broken solder joints. Re soldered that then my black and grey and fresh read full but the only one that was full was the fresh

This brought me to pull the sensors on the grey tank. I loosened the screws when wouldnt come out, lots of people just abandon them and drill new holes. Two of mine were seeping so opted to put a board against the tank get a wonder bar then pried and wiggled them out. They had about an 1/8” of solid black material on them. Opted for the sensors shown in pic #3 cheaper than the horst ones and i dont think any of the last forever it will be a maintenance item. New sensor got a dab of silicone on the outside surface of the tank.

Welp it worked my grey tank went from empty to full as the domestic went from full to 1/4 because that still has water I can see. I still have to replace the black tank sensors but its progress the only diode that doesnt light is the 3/4 full i believe the driver for that is smoked.
Going back to fix the clock fire hazard regulator now
Dave

[Vonhitch]

Here some pics of the voltage regulator on the clock its a LM317MP dont have one here so i just ordered some and I bought a heat sink for that. Ill have to come back to that when I get the part.

Pic #1&#2
show how the board was burning which IMO sure isnt good I suggest others look to see if they have this condition.

Pic #3 &#4
shows my set up. Its a cheap weller mat a syringe of flux and a $40 micro soldering iron off amazon have to supply your own what is basically a cell phone charger and cord

Pic #5 & #6 &#7 and the key #8
Shows the key to this kind of work. Soldering wick. What you do is flux the wick put it on the part you want to desolder and it pulls the solder into the wick see pic #7 the right side of that wick is full of solder. That pic also shows some white stuff left on the board from the regulator.

This said I know people say that propane fridges cause fires but I wonder how many fridges got blamed for something like this.. just something to consider.

Now I wait till thurs for the part. Hope this helps someone.
Dave

[Randy Dupree]

Very interesting,thanks for posting.