Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: TIMBO on August 25, 2018, 05:21:41 am

Title: VASE TRENDSETTER 40
Post by: TIMBO on August 25, 2018, 05:21:41 am

Hi guys, Another local built amp needs some attention, built around 1967.
(https://i.imgur.com/EJgF1Qf.jpg)
Missing a rotary power switch.
Old Ecaps need replacing.
General tidy up.
(https://i.imgur.com/W6nlkFH.jpg)
(https://i.imgur.com/6lLYfTX.jpg)
(https://i.imgur.com/OBYikbf.jpg)
(https://i.imgur.com/EPIjzPS.jpg)
So there is a problem...........
First, lots scratchiness on the pots of the normal channel, problem was the .047 cap was dodgy, replaced with temporary cap, problem sorted.
Second, compressed unpleasant distortion on notes, output volume not as loud as expected.
Checked mustered caps for faults and replaced the two tropical fish caps with good mustards.
No change.
Suspected OT may be faulty, did some checks and was unable to get good readings on taps, replaced with another OT.
No change.
Pulled trem valve
No change.
Pulled V2.
No change.
Replaced V2 and pulled V1
No change.
All new 12AX7s
 :dontknow:

Title: Re: VASE TRENDSETTER 40
Post by: kagliostro on August 25, 2018, 06:37:48 am

Ciao TIMBO

Quote

All new 12AX7s

Are you sure they are OK ?

Can you put on some tubes you know to be good for sure ?

Franco

Title: Re: VASE TRENDSETTER 40
Post by: shooter on August 25, 2018, 10:15:24 am

Quote

compressed unpleasant distortion on notes,

both channels ?

I can't find the (other) * for v2B pin 8, i'll keep lookin

Title: Re: VASE TRENDSETTER 40
Post by: kagliostro on August 25, 2018, 10:29:12 am

Quote

I can't find the (other) * for v2B pin 8 ...

on V1b pin 8 (common anode mixer) ?

Franco

Title: Re: VASE TRENDSETTER 40
Post by: shooter on August 25, 2018, 11:29:46 am

Thx K,
figured it was mixing, just couldn't find the cathode stuff  :think1:
that might be a mod once it's up, to un-share with V1b. 

Title: Re: VASE TRENDSETTER 40
Post by: kagliostro on August 25, 2018, 02:25:34 pm

Some options

(https://i.imgur.com/DF3G3X8.jpg)

(https://i.imgur.com/d50q4aH.jpg)

(https://i.imgur.com/X2VDk6N.jpg)

Franco

Title: Re: VASE TRENDSETTER 40
Post by: TIMBO on August 26, 2018, 04:19:34 am

Thanks Franco, I had thoughts that it was the way the two channels were mixing that was causing a problem.

After studying some photo's of other Vase and comparing with another vase I have, two 470k grid leak resistors were missing from V1b and V2b.
Adding these helped a bit .
Not sure why I tried this but I added a 2.2k/5w resistor to the power valve screen supply and this helped greatly.
The notes are more defined and chording aggressive.

(https://i.imgur.com/1gz7zPq.jpg)
(https://i.imgur.com/zidzCoY.jpg)