1973 DR 103 - amp on, no sound

[theWalrus]

Hi folks, it's been a while. How are you?

I haven't played through my 1973 DR 103 in a while because of a problem in the output of high frequencies (I couldn't hear 22nd fret high E bends, for example). I got a kit from HI-TONE to do a recap of the electrolytics, and I tested the amp yesterday. Amp on, not on standby, volume up, plugged straight in, but no sound. I normally use it with an attenuator and all connections were correct, but I also tested with the connections directly from amp to cab.

I'm planning to take it to a tech here in Phoenix AZ, but before I do so... I wanted to ask:

Is that problem maybe related to not playing through that amp in a while (maybe 6 months)? I hope it's not a blown transformer, but I've had a blown transformer in another 100W head before and I heard static rather than no sound.

My '79 Hiwatt cab had old wiring (that fell apart) and that blown transformer I mentioned was of a 1959HW Marshall, connected to it. It was a pain to get the original parts back and repaired, but I finally have it working, in addition to the cab. The Hiwatt head was used with that cab prior to rewiring, but also after rewiring, and it sounded fine, except for those high frequencies I mentioned. So, I'm skeptical it's the transformer or the electrolytic caps for the cause of no sound.

Have you had similar experiences?

Thanks

[OldSchoolDave]

Have you checked the speaker fuse with a meter?

Dave

[theWalrus]

Have you checked the speaker fuse with a meter?

Dave

Hi Dave,

Great suggestion; that could be it! I hope it is! There seems to be 2 fuses: 5A (main) and 1A --- I'm guessing the 1A is the speaker fuse.

Can I safely pull the fuse out (without removing the tolex) and check for DC current with a meter, or you suggest just bringing it up when I visit the amp tech?

Best regards

[OldSchoolDave]

Can I safely pull the fuse out (without removing the tolex) and check for DC current with a meter, or you suggest just bringing it up when I visit the amp tech?

We may be saying the same thing but, to be certain: The fuses are definitely "user serviceable parts", but you need to pull them out of the holder - while the mains cord is unplugged - and check for Continuity (DC Resistance = 0). If the fuse passes current, it should be good. The filaments can be difficult to troubleshoot visually, only the meter can tell for sure.

Note that, if your fuse has popped, it may be due to a greater issue. Things to check if the output fuse has sacrificed itself are:

Are all power tubes working and properly seated?
Are all contacts on the Impedance Selector free of oxidation and properly seated?
Are the speaker cabinet and cord known to be good?

If the answers are "Yes" and it still pops that fuse, it's Tech Time.

Dave