PACE MBT-250 / Vacuum pump issue?

[timbocgn]

Hi Pace Experts,

I have bought a used PACE MBT-250. It works pretty well for its age and it is fun to desolder!

What I notices, when pressing the vacuum button is that for the first millisecond the pump is pushing out air instead of sucking it. It is not really harming the desolder process, but I am thinking of getting rid of it.

Could it be that the pump valves are worn out? Would the Motor Pump Rebuild Kit 6993-0190 be a solution?

Thank you in advance,

Tim.

[richnormand]

I have a very old Pace desoldering and rework station that I got used. It was doing what you described but for a longer time. I ended up dismantling the vacuum pump and it was full of crud (despite the external filter).

Two points :
1)
cleaning the pump internals and removing sticky deposits (IPA) with crud (solder blub and ashes) on the seals on the flapper valves restored the vacuum
2)
the external filter was in need of change and was almost blocked going in the pump but free-er flowing in the wrong direction... It was changed (and still changed regularly) with a drip coffee filter insert (works great).

Other thing to look at is the path and seals at the wand itself. Free up any solder accumulation and check the tip and all the seals in the wand so you do not loose vacuum before the tip.

All said I still have a small brief puff back at the tip before a good vacuum is established but it does not alter performance.

Hope this helps.
Cheers.

[timbocgn]

Hi Rich,

Thank you very much - I will give it a try.

Cheers,

Tim.

[Shock]

Normal operation of these models is they snapvac (suck with extra pressure) for the first second. Ensure only the one tool air line is connected to the station. I leave the flow control knob wide open while using it.

The tool has a filter in the glass trap as well that requires changing regularly. Then two rubber grommets at either end of the trap dictate the air seal quality, only replace when needed. If you have a disposable cardboard trap replace it with a new one or just go for the reusable glass ones (setup properly). All these parts are quite cheap and can be found in the manuals and on Paces website, distributors carry them.

You can even get a pump rebuild kit, but as posted above if it's been run without the filters being changed or without them, give it an inspection and clean first.

[timbocgn]

Hi Shock,

thanks for your reply. I replaced the paper traps by a new glass trap (and new seals / filters). I also replaced the internal and external VisiFilter paper thingies. The vacuum itself is quite good.

The issue is really the first "puff" as Rich described it, which goes in the wrong direction. It is very short - not nearly as long as the snap vac period you mentioned.

I will clean the pump and then we will see - I have no idea if the former owners have used it without VisiFilter (it was not attached...).

Thank you!

Tim.

[asis]

Hi,

When disassembling, pay attention to the condition of the eccentric connecting rod i.e. bearing races.
This pump often breaks the plastic of the cage, as, in other matters, the race of the connecting rod bearing of the PACE ST325 vacuum pump.
It's impossible to glue it.
You have to make a semi-circular clip in the form of a bandage out of soft tin.

[timbocgn]

Hi Asis & others,

thanks for the hints. I disassembled the pump today and cleaned it with a lot of IPA. Unfortunately it did not fix the issue. 

In the first some milliseconds at the beginning of the pump activation, it is pushing out air. See this tiny little video:



I will order the rework kit and see if this fixes the issue!

Cheers, T.

[asis]

Something I don’t hear the characteristic pump acceleration at the first moment of time (SNAP-VAC), as @Shock writes about.
Could it be something in the motor control circuit?
+26V -> Q21 darlington p-n-p ; SManual page 59 Sheet 3.

It seems to me that you do not have enough vacuum to suck out the solder and for some reason some solder remains in the Desolder Tip shank, which should already be in the cartridge?
You should check the condition of the rubber cuffs in the SX tool itself.

The old style SX70/80 Desolder Tip (Endura) has a different shank design than the SX90/100 Desolder Tip.

For cleaning the Desolder Tip's there is a PACE tool P/N:6993-0200.

[timbocgn]

Hi Asis,

for the test video I filled the tip by intention with solder - otherwise it is hard to distinguish between vacuum and pressure.

As you could see, for a small period of time the pump produces pressure and then vacuum. Desoldering is possible, I can also her the sucking sound on the pcb and solder is in the chamber. The snap vac pump acceleration is there, it was just missing in the video.

It seems that the valves are worn out and do not close fast enough when the pump starts. I Ordered the kit today in Germany, got confirmation that the distributor has it available. Let's see if this fixes the issue.

Thanks so much for your efforts!

[Shock]

You always have and extras as spare parts anyway. But I'd strongly suggest contacting Pace and show them the video as they may already know the problem and what you need.

Further troubleshooting you may be able to disconnect the tool hose at the station or at the tool and use a piece of paper or something to see if there is a subtle movement like with the solder. Assuming you did what I said and disconnected other hoses and leave the air flow wide open, then try disconnecting the other tools, then use the other channel.

I forgot to mention in my other post the only other thing that can occur is the if the tip needs a clean or has baked on flux on the inside it can also reduce the airflow. In this below video 1m40s you can hear what snapvac sounds like. It's 1.2 seconds according to Billy.



In this video with the older model you can hear the snapvac and pump sound at 1m25s.

[xmris]

guys is this 'normal' on those desoldering pumps? I have the PACE Vf100 and the trigger has two functions: slight pressure blows hot air for preheating the solder point then pressing the trigger further to activate the pump function.

[timbocgn]

Hi Shock,

that's exactly the sound my MBT 250 makes when I press the button. So the snap vac feature works!

I also dropped PACE a mail to ask them about their opinion and I will do the test with the paper sheet when I am back home from the office ;-)

Cheers, Tim.

[timbocgn]

Hi guys,

to confirm the issue I did three videos:

1) Snap Vac

https://youtu.be/kogVqJkRWKc

Full recording of to pump activations - the snap vac sound is there.

2) Show the airflow / attempt #1

https://youtu.be/0u29Hn8j9cA

I tried to make the pump issue visible by placing some solder balls in a tube attached after the VisiFilter. It is hard to see but the one at the front move a bit to the left (pushed out) before all are sucked into the filter. It's hard to see.

3) Show the airflow / attempt #2

https://youtu.be/aIDTEHThF70

For this I placed a ball at the end of the input of the VisiFilter. You can clearly see that it is pushed out.

I also contacted PACE and a support engineer (thanks Tony!) confirmed that the rework kit is the right idea.

So lets wait until I get the kit.

Cheers, T.

[richnormand]

@timbocgn

Just a though.
Considering the initialisation of the pump does generate an initial outward burp the solution could be a one way valve in the hose.
Something like this:

https://www.amazon.ca/Check-Valves-Aquarium-Stainless-Non-Return/dp/B07STW5JY8/ref=asc_df_B07STW5JY8/?tag=googleshopc0c-20&linkCode=df0&hvadid=578834357451&hvpos=&hvnetw=g&hvrand=6269460476683820737&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9000663&hvtargid=pla-1639480068880&psc=1

for aquariums.

It would stay closed until a suitable vacuum has been established before opening (depending of the spring strength).... of course that might cause a slight delay but should eliminate the spit back.

It is probably not an issue for my system since I usually operate the vacuum a few seconds before shutting down to ensure the tip does not get clogged down.

[asis]

Hi timbocgn,

I don't think replacing the pump diaphragm will do anything.
When you dismantled the pump, you did not pay attention to the fact that someone else was doing it besides you.
I want to know - the engine was soldered, judging by the handwriting of the actions?
You need to try to reverse the motor by changing the polarity.
Because at the first moment, the operation of the diaphragm bypass valves may depend on the direction of rotation of the piston eccentric.

The sound of the pump is not convincing.
Maybe the motor is not original (?).

[asis]

When changing the polarity, be careful - a damper diode may be soldered on the motor.
The position of the eccentric when tightening the fixing bolt may also matter.

[timbocgn]

Hi guys,

I promised a feedback - here we go:

https://youtu.be/R3b2uCinyNw

As you can see, no more pushing just pure vacuum.

Changing the valve sheet and the pump housing was the solution (using the https://paceworldwide.com/motor-pump-rebuild-kit rebuild kit) . The new one is black instead of white (see picture).

I could not resist to take the old housing apart (I was not brave enough before, it really sticked together) and you can see the issue. A lot of dirt and quite wobbly valve sheet. I will keep these as spare parts.

Thank you all for your support!

Cheers,

Tim.

[Wallace Gasiewicz]

timbocgn:

Thank you for posting your work, I think it will help me and others.

[richnormand]

It does look a lot like mine did before cleaning.
Been running OK for the past decade apart for that very brief puff that I mentioned previously. So I am not complaining!
Thanks for posting feedback on the issue.
Cheers and happy desoldering.

[tooki]

guys is this 'normal' on those desoldering pumps? I have the PACE Vf100 and the trigger has two functions: slight pressure blows hot air for preheating the solder point then pressing the trigger further to activate the pump function.

The VF100 is a really strange model which I'm nearly 100% certain is a custom/rebadged Den-On Instruments. It looks like it's based on the SC-400A desoldering station, but with the digital temperature controller from the SS-8300 grafted in.

Is yours made in Japan?


As for "is this normal"? No, on the "real" Pace desoldering irons, they don't puff air first. They have the "snap-vac" where it takes a big gulp of air (by first giving the pump a higher-voltage pulse) before continuing to pump at normal speed.

[Haenk]

I had the same issue with the initial push of air. Cleaning the rubber seal inside the pump did not really help, it wasn't that dirty anyway.. Unfortunately, the service kit including a new seal is quite expensive for what it is and difficult to source  - got a new spare pump on ebay for a bit less than that. This solved the issue.