Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: DLPublic on June 30, 2016, 04:55:05 am

Title: OT fibre washers - where do they go?
Post by: DLPublic on June 30, 2016, 04:55:05 am

My output transformer has two fibre washers along with one flat and one shake proof washer per fixing bolt.

I presume one of the fibre washers is placed between the bolt head and the metal cover at the top of the OT, but where does the other one go?

Dave

Title: Re: OT fibre washers - where do they go?
Post by: uki on June 30, 2016, 08:33:57 am

Hi there!

Lots of installation instructions in this link: http://el34world.com/Hoffman/instructions.htm (http://el34world.com/Hoffman/instructions.htm) 

Title: Re: OT fibre washers - where do they go?
Post by: DLPublic on June 30, 2016, 11:03:04 am

Uki,  have already read (and re-read) that info but it does not answer my question.  Also have tried a search for fibre (and fiber) washers and output transformer which proved fruitless.  I have also emailed the supplier of the transformer, but as yet no reply.   :help:

Dave

Title: Re: OT fibre washers - where do they go?
Post by: shooter on June 30, 2016, 11:10:33 am

Quote

but where does the other one go?

I'm looking at an OT setting on my desk, it has 4 bolts holding the end-bells on, each is;
fiber washer, plastic sleeve on screw *head* side.  the other is plastic sleeve, fiber washer, metal washer, nut.
not sure if that helps

Title: Re: OT fibre washers - where do they go?
Post by: sluckey on June 30, 2016, 11:17:20 am

Quote from: DLPublic on June 30, 2016, 04:55:05 am

My output transformer has two fibre washers along with one flat and one shake proof washer per fixing bolt.

I presume one of the fibre washers is placed between the bolt head and the metal cover at the top of the OT, but where does the other one go?

Dave

Is your OT not bolted together?

Normally you would put one fiber under the bolt head, shove the bolt thru the OT, then place a fiber, followed by a flat, followed by a star, followed by a nut on the other end of the bolt.

Title: Re: OT fibre washers - where do they go?
Post by: DLPublic on July 01, 2016, 11:49:49 am

Thanks all for your comments.

I have had a response back from the OT supplier and he agrees with Sluckey.  It is supposed to prevent the bolt making a shorted turn through the stack but that also requires the bolts to be insulated from the edges of the holes in the chassis, which mine are not!

Hope that is not an issue.

Title: Re: OT fibre washers - where do they go?
Post by: EL34 on July 03, 2016, 04:34:32 pm

That's goofy
Who ships transformers with the insulation washers not installed?

The manufacture installs them when they assemble them

Title: Re: OT fibre washers - where do they go?
Post by: DLPublic on July 04, 2016, 12:03:56 am

Quote

That's goofy
Who ships transformers with the insulation washers not installed?
The manufacture installs them when they assemble them

They were installed, that is how I knew where the top one went.   However was not sure whether the bottom one should be above the chassis, I.e. directly underneath the OT, or below.  Turns out it is below.