howling GB5...

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howling GB5...

Postby Jimmy Oneschuk on Tue Apr 03, 2007 5:32 am

Howdy folks,

Anyone out there with a GB5/FB80 that's experienced high-pitched howling coming from the groups (or the expansion valve, I think) during autofill and while running shots? It sounds a lot like having air trapped upstream in a pipe, while water's being drawn out downstream...

This is the latest problem I've had with the GB5. It didn't work out of the box; it was offline for about a week awaiting parts to replace a failed steam element (due to crossed wires on the control board from the factory). Worked great for two days after new parts arrived, now it's offline yet again.

-jimmy
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Postby paul_pratt on Tue Apr 03, 2007 4:39 pm

It's almost certainly the expansion valve. You will hear a high pitch squeel when pulling a shot. Just adjust by turning the brass body. Remember you want a small consistent drip around 11-12 bar. Assuming your brew pressure is ok and inlet pressure stable, the groups were bled etc.. you may just need to tweak it a little either way - sometimes the sping vibrates at a certain pressure. I don't think I've ever had to replace the spirng and gasket on these as normally a little tweak works. New machines come with the expansion valve undone so they can drain it before shipping, that has to be set properly during installation.

The machine has two check valves inside and one on the pump. Sometimes these can make a small noise but nothing like an expansion valve squeal. You will really only notice these when you first install the machine or when autofil kicks in.

Let us know how you get on.

Paul
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Postby Jimmy Oneschuk on Wed Apr 04, 2007 6:26 am

What's weird about this situation, is the howling from the expansion valve only began on monday this week. After the steam element blew out, then was replaced and the wires connected on the control board properly, the machine was running fine for two days before the howling began.

Thanks for the tip though - I'll see if I can put it to work. My service tech was away at a funeral yesterday.

Cheers,
Jimmy
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Howling

Postby roger on Wed Apr 04, 2007 2:21 pm

I have to agree 100% with Paul. Howling is almost without exception caused by an incorrectly adjusted expansion valve. If there is a question, just throw a PF with a blind insert into a group and observe the expansion valve while the group is on. Assuming that your dispensing pressure is adjusted correctly (9 bar) you should see no water flowing from the expansion valve.

As a side note, there is no relation between the expansion valve and the steam boiler, so, the second issue could not have been brought on by the first.

Sincerely,

Roger
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Postby Jimmy Oneschuk on Wed Apr 04, 2007 8:07 pm

Thanks Paul - after I read your post, I played around with this a bit on my own and started to get somewhere. Then Vince called me and walked me through the fix. What I didn't understand was that you need to adjust the valve in tandem with the pump. Needless to say, I spent the rest of the day pulling beautiful shots.

I couldn't be a happier barista; I can now focus on promoting my business. Lemme tell you, I was pretty stressed out during the whole ordeal with 50lbs of coffee sitting around (yes, I had my home e61, but there's really no comparison between the 2 machines in the commercial environment).

Anyhow, thanks for all your help!
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Re: howling GB5...

Postby Phuong on Fri Jun 27, 2008 10:19 pm

Hi guys,

Thank you so much for this info! A couple of my groups started producing these high-pitched squeals intermittently. I was so glad to find this thread. After reading this, I also consulted the LM orange manual and found the same solution in there WITH pictures too :) .

Jimmy - Thanks for mentioning that you needed to adjust the valve and the pump in tandem.

No squeals now…. I so happy!!!(This sentence should be spoken with oriental accent for the full affect)

Phuong
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