Need some help and advice - amp smoking!

[DT999]

I was happily listening to records this evening when we suddenly had a power outage that affected the whole street, but only lasted about 20 - 30 seconds.

I managed to get to My TT  and lift the tonearm, but when the power came back on and the amp was turned on it started billowing smoke from the rear near to the power cable.

I'm not sure why this occurred or what has happened as our power box has proper RCD breakers and my equipment is connected via a Thor surge protector.

I immediately turned it off and disconnected the power lead, but am wondering what damage might have occurred and what I should now do.

It is a Modwright LS100 valve amp.

I am guessing at the least I need to get the amp checked out for potential damage, whatever that may be.

Does anyone have any suggestions as to a competent tech anywhere in the Geelong  region?

Thanks Derek

[Blood_Red_Bird]

Keep a record of the event.... date, time & repair receipt etc

We had a Monitor fry in similar circumstances recently

& received a full payout from the energy supplier

[stereo coffee]

1 hour ago, DT999 said:

I was happily listening to records this evening when we suddenly had a power outage that affected the whole street, but only lasted about 20 - 30 seconds.

I managed to get to My TT  and lift the tonearm, but when the power came back on and the amp was turned on it started billowing smoke from the rear near to the power cable.

I'm not sure why this occurred or what has happened as our power box has proper RCD breakers and my equipment is connected via a Thor surge protector.

I immediately turned it off and disconnected the power lead, but am wondering what damage might have occurred and what I should now do.

It is a Modwright LS100 valve amp.

I am guessing at the least I need to get the amp checked out for potential damage, whatever that may be.

Does anyone have any suggestions as to a competent tech anywhere in the Geelong  region?

Thanks Derek

Hi Derek

Your Modwright is designed for 120v @ 60Hz  , you should be using a step down transformer from Australian  voltage  240v to 120v, but that is not mentioned in your post.   http://www.modwright.com/cms/resources/1491927986ls100ownersmanualfinal.pdf

 

Given your observations,  there is certainly damage to the Modwright transformer, and likely other parts too. It might be best to return it for repair, as often parts are quite specific, and need to be returned to factory spec.    EMAIL: modwright@yahoo.com . 

[Pops110]

Hi Dereck, I would be definitely getting it checked out before you turn it on again. Sorry I don’t have any recommendations for your area. There is a thread with repairers on SNA might be able to find someone on there.

I nearly bought an LS 100 a little while ago, supposed to be very good amps. 

No step down transformer required mate.
 

Absolute Hi End are the distributors, may be worth shooting them a message and see who they recommend. 
https://absolutehiend.com/contact-us/

[DT999]

21 minutes ago, stereo coffee said:

Hi Derek

Your Modwright is designed for 120v @ 60Hz  , you should be using a step down transformer from Australian  voltage  240v to 120v, but that is not mentioned in your post.   http://www.modwright.com/cms/resources/1491927986ls100ownersmanualfinal.pdf

 

Given your observations,  there is certainly damage to the Modwright transformer, and likely other parts too. It might be best to return it for repair, as often parts are quite specific, and need to be returned to factory spec.    EMAIL: modwright@yahoo.com . 

Thanks Chris, I wasn't aware of the need for a step down transformer! I will certainly contact Modwright for advice

[Pops110]

3 minutes ago, DT999 said:

Thanks Chris, I wasn't aware of the need for a step down transformer! I will certainly contact Modwright for advice

If you’ve been using it you definitely won’t need a step down transformer, they are bought into Australia by Absolute Hi End so will be 240v.

[Nada]

27 minutes ago, stereo coffee said:

Hi Derek

Your Modwright is designed for 120v @ 60Hz  , you should be using a step down transformer from Australian  voltage  240v to 120v, but that is not mentioned in your post.

 

What makes you assume that? Hes been happily running his amp in Geelong. The problem came after  blackout presumably preceded by an over-voltage event.

[Nada]

1 hour ago, DT999 said:

Thor surge protector.

 

Which one?

 

Anything else blow at your place or with the neighbours?

[DT999]

2 minutes ago, Nada said:

 

Which one?

 

Anything else blow at your place or with the neighbours?

Thor A12BF Smart Board 8, nothing else on the board blew and neighbours had no issues as far as I know

[Nada]

1 hour ago, DT999 said:

but am wondering what damage might have occurred

 

Is it worth lifting the lid to see whats smoked?  Maybe not if  it needs to go in for qualified repairs but it would be good to see if its salvageable.

 

Maybe forget the repair hassle and just see if the power company will pay for the pre-amp  as a right off. Is it worth phoning them right away and get  job number to strengthen your case?

 

[Nada]

7 minutes ago, DT999 said:

Thor A12BF Smart Board 8, nothing else on the board blew a

• Clamping voltage 300VAC
• Reaction time less than 1 nanosecond

Bad luck.

[DT999]

8 minutes ago, Nada said:

 

Is it worth lifting the lid to see whats smoked?  Maybe not if  it needs to go in for qualified repairs but it would be good to see if its salvageable.

 

I can certainly take cover off as I've done that to change tubes but I'm not really sure what I would be looking for.

I will contact the power company, but I don't hold out much hope having read their policy on reimbursing damage, but will try. Might also have a look at my home insurance, but ideally I need to get it checked.

It seems as though the distributor Pops110 mentioned are in Melbourne and seem to have a repair centre so I will check with them after Easter.

8 minutes ago, Nada said:

 

 

[muon*]

Surge protector boards are not the great protection people are lead to think they are, and the guarantees on the packaging is not worth a pinch either.

[muon*]

38 minutes ago, Pops110 said:

If you’ve been using it you definitely won’t need a step down transformer, they are bought into Australia by Absolute Hi End so will be 240v.

Yup, would have failed quick smart on first power up if it was spec'ed for 120vac

[Nada]

1 hour ago, DT999 said:

I can certainly take cover off as I've done that to change tubes but I'm not really sure what I would be looking for.

 

Id be looking for where the smoke came from. Anything that looks blackened, melted, smoke stained. Then Id have a good look at the PCB traces. Then Id post photos of anything suspect so the resident brains can guide you.

 

Maybe it will be a simple fix?

Edited April 17, 2022 by Nada

[muon*]

As above, and that means both sides of the PCB if possible. If it has a removable bottom cover/plate

[DT999]

Thanks. I will try and have a look tomorrow and post a few pics of what I find.

 

 

[DT999]

OK,  I am hoping this might not be as bad as I feared. Firstly I confirmed that the unit is designed for 240v, it is clearly labled on rear.

I have taken the cover off and can see no obvious signs of damage or burning, but I did notice a fuse inside next to the power inlet which is the area where the smoked came from.

Initial examination of the fuse looked as though it hadn't blown, but under magnification it looks as though the fuse has a solid metal rod with fuse wire wrapped around its length, and this certainly looks melted. So much so it appears like small solder blobs inside the glass tube.

So I am hoping the fuse did its job and this might be the only problem?

Does anyone have any other thoughts?

Thanks

Derek

Edited April 18, 2022 by DT999

[DT999]

Looking up specifications it looks like a 1.5A 250V slow blow fuse that I need

[bob_m_54]

The fuse is constructed with glass fibres to support the fuse wire element, which is wrapped around the support. And yes, easily visibly ruptured. But.... that doesn't explain the smoke and the reason for the excessive current draw which caused the fuse to blow, unfortunately.

[DT999]

2 minutes ago, bob_m_54 said:

The fuse is constructed with glass fibres to support the fuse wire element, which is wrapped around the support. And yes, easily visibly ruptured. But.... that doesn't explain the smoke and the reason for the excessive current draw which caused the fuse to blow, unfortunately.

Thanks Bob. I am presuming the issue was caused by a power surge in the grid which knocked the whole street out for 20-30 seconds. It happened again about 15 minutes later for about a minute and then a third time a bit later with power out for half an hour. There was certainly something going on with supply, so I am guessing the first spike was the cause as when power came back on that was when there was smoke.

 

The fuse glass does look a bit blackened inside near, I was wondering if that would cause the smoke I saw? It was coming out of the case in exactly the same place as the fuse, and I can't see any other burn indications or damage inside the amp.

 

Is there anything else I should check? Is it worth getting a fuse and powering up to see what happens or could that cause more damage, I  really don't know.

[bob_m_54]

No, the fuse would not cause the smoke. Even when violently ruptured, you get the glass envelope shattering with a bang, and blackening around the area, but no noticeable smoke.

 

What can happen too is when you get a power interruption, you can actually get a "brownout" which is a Low Voltage condition. Then when the power comes back on you get a spike, or High Voltage condition. Combine these two together and it can cause some weird failures. Generally things with motors are more affected, but that is the exact condition that killed my Tektronix Oscilloscope, part way through completing an assignment that was due to be handed in the next day .

[DT999]

7 minutes ago, bob_m_54 said:

No, the fuse would not cause the smoke. Even when violently ruptured, you get the glass envelope shattering with a bang, and blackening around the area, but no noticeable smoke.

 

 

Thanks, I will contact the distributor repair centre and see what they advise, might need to send it in for inspection just to be sure.

Edited April 18, 2022 by DT999

[Nada]

It will be annoying to ship the pre-amp interstate for service ,  if all it needs is a new fuse.

 

A local tech might be a first step?

 

I wonder if any techs would start a test with a lower rated or fast blow fuse to be safe, and/or a variac,  or would they just insert the usual fuse and stand well back?

[bob_m_54]

you could try replacing the fuse, as long as you're prepared to risk further damage. Doing anything else yourself could be risky to yourself and the equipment, if you aren't familiar with working on electronics equipment, especially in the mains supply area.