Recent Posts

31

Tube Amp Building - Tweaks - Repairs / Re: Carlsboro tube reverb noise/Hiss

« Last post by Yosser on March 10, 2026, 02:18:37 pm »

The circuit is independent apart from it's power supply, a bit like a send and return module - if it's turned off you can't hear the hiss.
If anybody has experience of this amplifier they may be able to tell me if this noise normal?

32

Tube Amp Building - Tweaks - Repairs / Re: Tube ID

« Last post by Rontone on March 10, 2026, 01:00:46 pm »

May be it is a 1958 Philips (from Holland)

Yeah, the construction does look very much like Philips type, the mica spacers and plates

33

Tube Amp Building - Tweaks - Repairs / Re: Tube ID

« Last post by kagliostro on March 10, 2026, 12:35:12 pm »

May be it is a 1958 Philips (from Holland)

Consider the prints

2A1

AH8

Franco

34

Other Topics / Re: Meme of the day

« Last post by shooter on March 10, 2026, 12:34:19 pm »

....

35

Tube Amp Building - Tweaks - Repairs / Re: Tube ID

« Last post by pbman1953 on March 10, 2026, 11:58:17 am »

How's the brand?

36

Tube Amp Building - Tweaks - Repairs / Re: Tube ID

« Last post by Rontone on March 10, 2026, 11:56:36 am »

Those codes do look very similar to european codes and the stamping, the tall font looks a bit like some Brimar or the Mazda branded Brimars

37

Tube Amp Building - Tweaks - Repairs / Re: Tube ID

« Last post by pbman1953 on March 10, 2026, 11:39:04 am »

Here'd a couple more close ups


One is a hand written and other possibly stamped other someone with a really steading hand.

38

Tube Amp Building - Tweaks - Repairs / Re: LOW Output from 50's GA20

« Last post by Rontone on March 10, 2026, 11:27:24 am »

http://www.geofex.com/ampdbug/outtrans.htm

Here's a guide that explains a few more test methods for output transformer secondaries

39

Tube Amp Building - Tweaks - Repairs / Re: LOW Output from 50's GA20

« Last post by Yeatzee on March 10, 2026, 11:22:18 am »

What's the AC voltage on the primary when you inject 3VAC on the secondary?

100v on the primary = 2.6v on the secondary. I've been told a decent drop on the secondary from input voltage indicates a misbehaving OT secondary. Is that not the case?

40

Tube Amp Building - Tweaks - Repairs / Re: LOW Output from 50's GA20

« Last post by Yeatzee on March 10, 2026, 11:20:48 am »

Altering the design of the amp by changing component values is not a troubleshooting technique.

I've not run into an amp that ran the screens so low compared to the plates so I decided to just experiment and get it closer, still a big drop with the 2.2k. Obviously that wasn't the fix either way, more of an aside than anything