Bottlehead Forum

Bottlehead Kits => Crack => Topic started by: martymcmuck on June 01, 2023, 09:29:53 AM

Title: No Audio, odd voltage readings.
Post by: martymcmuck on June 01, 2023, 09:29:53 AM

I'm trying to repair a crack that stopped functioning a few years ago.

It's a 240v.

I started by powering it on according to the manual, and started with a voltage check not according to the manual.

The only terminals giving a voltage reading that's not zero are

13-246v
15-246v
21-245v

Now, I should started from the start and done the resistance readings first...

Resistance readings are

3-0
6-2.45k
7-2.8k
8-0
9-2.8k
10-2.46k
12-0
13- Massive spark.

Testing ceased at 13 and here I am...

As a note, the unit functioned well for a few years before not functioning.

Any suggestions, please and thank you?

Title: Re: No Audio, odd voltage readings.
Post by: Paul Birkeland on June 01, 2023, 12:46:25 PM

What are the voltages at terminals 1-10? 

If you check the resistance at terminal 13, the amp needs to be off and you need to be sure there's close to 0V DC at terminal 13.  Because you have 245V at terminal 13, measuring the resistance at terminal 13 is unlikely to present any issues.

In what way does the Crack not function?

Title: Re: No Audio, odd voltage readings.
Post by: martymcmuck on June 02, 2023, 07:41:33 AM

Voltage between 1-10 is zero.

The unit was powered off during the resistance check, albeit for only a few hours.

Prior to the large spark when testing resistance on 13, the tubes glowed but the unit did not produce audio, nor could I hear the faint noise floor, or the tubes warming up. Total silence.

Since the spark on 13, the tubes no longer glow.

Title: Re: No Audio, odd voltage readings.
Post by: Doc B. on June 02, 2023, 07:47:27 AM

If nothing works since the spark including the heaters, start by checking the fuse in the IEC socket.

Title: Re: No Audio, odd voltage readings.
Post by: martymcmuck on June 02, 2023, 08:09:18 AM

I replaced the fuse and still no glow.

Triple checked that it's plugged in, switched on. Tried a third fuse. Still no glow.

Title: Re: No Audio, odd voltage readings.
Post by: Doc B. on June 02, 2023, 08:49:09 AM

I would suggest performing the power transformer secondary tests on page 29 of the manual next to verify that power is getting to and through the power transformer.

Title: Re: No Audio, odd voltage readings.
Post by: martymcmuck on June 02, 2023, 09:35:53 AM

Thanks Doc.

The manual I'm using now is dated December 2013, downloaded from a forum and page 29 seems to be different. I purchased and built the unit back in 2011/2012 and the CD is long lone. Is there a way to download the manual version you're referring to?

Title: Re: No Audio, odd voltage readings.
Post by: Paul Birkeland on June 02, 2023, 09:48:49 AM

Terminal 13 connects to B5, B5 connects to B2, B2 connects to terminal 2, terminal 2 connects to terminal 4.

You have high voltage at terminal 13, what do you have at B2, B5, T2, and T4?  One of them is not connected to the others.