Bottlehead Forum

Bottlehead Kits => Legacy Kit Products => Crack-a-two-a => Topic started by: XforceVesa2 on November 03, 2019, 08:49:51 AM

Title: Power Transformer Secondary Test
Post by: XforceVesa2 on November 03, 2019, 08:49:51 AM

Hi Community,

I'm currently Building the Bottlehead Crackatwoa Amp.

I'm currently at the "Power Transformer Secondary test" part and have possibly found a problem.

I've wired the Transformer as "Greater than 225 VAC , less than 235 VAC" as I've measured 235 VAC on the IEC Inlet just before I've wired my Transformer.

The problem is that I've measured at the last Test(on the Terminals 20 and 19) 170,85 VAC instead of 161 VAC +/- 5%. Im not sure if this is a Problem or not and hope that somebody can help me with that Question.

Thanks in advance(Sorry for my bad English , it's not my first language)

Title: Re: Power Transformer Secondary Test
Post by: grufti on November 03, 2019, 11:20:34 AM

171 VAC is not that bad. It's only +6% instead of +5%.

Title: Re: Power Transformer Secondary Test
Post by: Doc B. on November 03, 2019, 11:29:40 AM

Yes, that's fine.

Title: Re: Power Transformer Secondary Test
Post by: XforceVesa2 on November 03, 2019, 11:34:25 AM

Thanks for the Answers.


I've kept going and passed the Glowing Test , so far so Good :D

Edit:

Is it normal that the Plate is slightly bend from the weight of the Transformer?

Title: Re: Power Transformer Secondary Test
Post by: Paul Birkeland on November 03, 2019, 11:55:59 AM

Quote from: XforceVesa2 on November 03, 2019, 11:34:25 AM

Is it normal that the Plate is slightly bend from the weight of the Transformer?

Be sure that the power transformer hardware is all properly mounted.  If a couple of those white nylon shoulder washers are missing or placed improperly, that can bend the plate.

Also aluminum sheet is extruded and wound onto a huge roll before it's then cut up into smaller pieces later.  It's not abnormal to find that a sheet will have some curl to it for a while, but eventually it should flatten out.

Title: Re: Power Transformer Secondary Test
Post by: XforceVesa2 on November 03, 2019, 12:04:21 PM

The Nylon wahsers seem to be mounted correctly , the plate is just slightly bend.

Maybe the plate was a little bend before the Mount of the Transformer and I just didn't noticed this earlier.

Title: Re: Power Transformer Secondary Test
Post by: Paul Birkeland on November 03, 2019, 12:28:00 PM

Yeah, if the power transformer is tightly mounted, that part of the plate won't be allowed to bend because it is rigidly mounted to the power transformer.  I have the production prototype Crack-a-two-a that's the oldest one, and the chassis plate is still nice and flat.