Silverface Fender 12AT7 burns ! (reverb)

Why does this 12AT7 burn ?

Burnt transfo

 

Cathode resistance value too low !

 

Please see my post on my other web site here : http://www.it11audio.com/amp/

 

 

Posted in Amps, Music Gear | Leave a comment

Xits X4

Nice amp on the bench ! A kind of Vox AC4 with excellent components (Mercury Magnetics transformers, SoZo capacitors ….)

Xits_X4

P1090181

P1090182

Posted in Amps, Music Gear | Leave a comment

Hiwatt DR103 : crunch mode mod !

Here is an Hiwatt DR103 a customer wanted to be modded « a la Jimmy Page ».

I proposed a slightly more easy and reversible mod … So, here we go !

Posted in Amps | Leave a comment

Marshall JCM900 2100SLX less bright mod

As many Marshall, the JCM900 2100SLX sounds VERY bright, outch !

So, I removed the 1nF bright cap (called …R22 !!!) and that is how it sounds now :

Easy mod, you can even cut one leg of R22 !

JCM9002100SLXPreamp(Ugly / poor readable schematic)

Posted in Amps | Leave a comment

Carslbro 50 TOP

I got this Carslbro 50 TOP to fix (burnt OT).

Carlsbro-50TOP

OT : Drake 784-213 (4.4k Zaa)

Carlsbro-50TOP-PT-Drake

Schematic (thanks Chambonino !)

 50-top-Schematic

The point is : on « my » 50 Top, power supply is quite different : PT has a central tap and no bias tap.

50-top2

On this 50 Top, power supply conforms to the schematic

Carslbro50TOP-CT

The 50 Top I have to fix …

50TOP-PCB

So, I retraced its schematic :

50TOP-PSU

I replaced electrolytic capacitors, OT (Hammond 1750N, 3.2k Zaa for JMP50) and 47k bias replaced by a 100k variable resistor

Carlsbro-50TOP-Bias

It plays loud with great crunch. Nice vintage amp !

Posted in Amps | Leave a comment

Stramp 2100A

As used by Rory Gallagher and Leslie West …
Stramp100W

Actually, even if Rory played on Stramp amps, I’m not sure he used this model …

Stramp2

Huge capacitors and transformers …

Stramp3

‘70s PCB, that can be accessed from inside and outside the chassis …

Stramp4

 

Stramp schematic

Stramp

 

Did you notice how the standby works ? High voltages are always there when the amp is ON. When on standby, the Phase Inverter input goes to the ground.

 

OK, guyz, this amp sounds loud !

Posted in Amps | Leave a comment

Vampower

vampower-100W

 

vampower

 

vampwire2a vampwire2b vampwire2c

 

(thanks to http://www.chambonino.com)

sound_of_the_70s

See http://www.vampower.com for more information

 

Posted in Amps | Leave a comment

Miles Platting amp

I got this amp for a complete check-up. 50W, 3 x 12AX7, 2xEL34, 1 GZ34

End of ‘60s, beginning of ‘70s I think …

 

MilesPlatting

MilesPlattingElectronic

MilesPlattingWilsic Miles Platting amps were made by Wilsic

 

Here is a Wilsic 50W (picture from the very nice http://www.chambonino.com site, thanks to him !) :

Wilsic50W

 

Now, let’s compare under the hood :

Wilsic50WChassis

Wilsic 50W (picture from Chambonino, thanks again)

 

MilesPlattingChassis

The Miles Platting : a capacitor is missing. Is it « by design » or a previous mod on this amp ?

 

Anyway, a good sounding vintage british amp !

Posted in Amps | Leave a comment

Fender Bassman Silverface circa 1967

A nice Bassman to check :

Fenders

From top to bottom : Bassman ’67,Bandmaster ’68, Bassman 100 ‘75

 

bassman_ab165_layout

bassman_ab165_schemP1050891 P1050892 P1050893

Earth OK, no Deathcap : good !   AB165 schematic

 

DripEdge, blacklines, Schumacher (606) transformers and choke from 1966 and 1967 :

SerialChassis

transfos1 transfos2 transfos3

 

tubesOld preamp tubes still well and alive !

Bassman recap’ed, bias checked with new power tubes (there is not bias pot on this model), hum balance set, let’s rock !

 

 

 

Posted in Amps | Tagged | Leave a comment

Beer + OD

Just for fun …

IT-11_Audio_OD1 IT-11_Audio_OD2

Posted in Pedals | Leave a comment