Mojotone kit Super Reverb

Amp tinkerers and people who aren't afraid of 700 volts or so in here....

Moderators: Slowy, Capt. Black

User avatar
sizzlingbadger
Vintage Post Junkie
Vintage Post Junkie
Posts: 8241
meble-kuchenne.warszawa.pl
Joined: Sat Jan 15, 2011 7:12 am
Location: Wire Wrapper
Has liked: 1202 times
Been liked: 1398 times

Re: Mojotone kit Super Reverb

Post by sizzlingbadger »

Photos in the previous post aren't working for me.
Tube amp and guitar tones straight from 1958… amazing how believable the sounds were back then, even without the modellers...

User avatar
Cdog
Vintage Post Junkie
Vintage Post Junkie
Posts: 4363
Joined: Wed Feb 07, 2007 3:01 pm
Location: Christchurch
Has liked: 3465 times
Been liked: 711 times

Re: Mojotone kit Super Reverb

Post by Cdog »

sizzlingbadger wrote:Photos in the previous post aren't working for me.
Ohhh... thanks. Tried again, do they work now? I've started experimenting with google photos, but having teething problems

User avatar
sizzlingbadger
Vintage Post Junkie
Vintage Post Junkie
Posts: 8241
Joined: Sat Jan 15, 2011 7:12 am
Location: Wire Wrapper
Has liked: 1202 times
Been liked: 1398 times

Re: Mojotone kit Super Reverb

Post by sizzlingbadger »

nah still broken, just little blue question marks. The last post was ok though.
Tube amp and guitar tones straight from 1958… amazing how believable the sounds were back then, even without the modellers...

User avatar
Bg
Site Admin
Posts: 43187
Joined: Fri Sep 05, 2003 12:13 am
Location: Auckland
Has liked: 2254 times
Been liked: 3873 times

Re: Mojotone kit Super Reverb

Post by Bg »

not working for me either, I suspect I need to be signed in to view them maybe?
So, is that low alcohol or no alcohol at all? mmmm, no alcohol, do you want to try it? Noooooooooo.

User avatar
Cdog
Vintage Post Junkie
Vintage Post Junkie
Posts: 4363
Joined: Wed Feb 07, 2007 3:01 pm
Location: Christchurch
Has liked: 3465 times
Been liked: 711 times

Re: Mojotone kit Super Reverb

Post by Cdog »

Bg wrote:not working for me either, I suspect I need to be signed in to view them maybe?
Thanks. Tried moving the pics to a shared folder and embedding from there... if no fix, I'l have to go back to imgur. :(

User avatar
Bg
Site Admin
Posts: 43187
Joined: Fri Sep 05, 2003 12:13 am
Location: Auckland
Has liked: 2254 times
Been liked: 3873 times

Re: Mojotone kit Super Reverb

Post by Bg »

first few are still fubar'd, last post of previous page is good :)
So, is that low alcohol or no alcohol at all? mmmm, no alcohol, do you want to try it? Noooooooooo.

User avatar
Cdog
Vintage Post Junkie
Vintage Post Junkie
Posts: 4363
Joined: Wed Feb 07, 2007 3:01 pm
Location: Christchurch
Has liked: 3465 times
Been liked: 711 times

Re: Mojotone kit Super Reverb

Post by Cdog »

Facebook hosted
Cdog wrote:Sorry more spam.

Check out the differernce in size of the transformers between the Spidervalve and the Super Reverb!
Interestingly, both are rated 40W and use 2x6L6 power tubes. The Mojotone trannies are pretty much double the size and weight.

PT
Image

OT
Image

I read that the Super Reverb version of the AB763 came with bigger Trannies that the other 2x 6L6 versions.
Scuse me while I geek out.

Spidervalve gutshot for more geeking: I suspect it needs new 6L6s, this will be a project for another day :)
Image

User avatar
Cdog
Vintage Post Junkie
Vintage Post Junkie
Posts: 4363
Joined: Wed Feb 07, 2007 3:01 pm
Location: Christchurch
Has liked: 3465 times
Been liked: 711 times

Re: Mojotone kit Super Reverb

Post by Cdog »

Time for a progress report. A couple of hiccups, and the Christmas New Year disruption have caused delays.

Hiccups:
I received the wrong layout fibreboard, and the kit was missing chassis straps. Mistakes happen, it's how they're put right that counts. No points lost for Mojotone there. Fibreboard arrived, chassis straps haven't yet but have been shipped.

Musings:
* I fitted an IEC power socket with internal fuse instead of the fixed cord and separate fuse 3AG holder. :thumbup:
* It is going to be very heavy! No chance an alloy chassis could handle those transformers, steel is a must.
* Difficulty on this one is definitely 5/5 (as advertised). I'm going to have to heavily annotate the schematic and layout, they're pretty minimalistic. (attached)
* Having a little grumble about eyelet fibreboards in general... flimsy and wretched things, I was spoilt with turrets on my last build. My current issue is trying to predrill the mounting holes for this fibreboard. I'm grumbling because there's not really much space to put mounting screws in the best places, and the board is so flimsy it'll need several. Most of the holes were predrilled, just not the eyelet boards mounting holes... obviously due to different layouts etc, the chassis is also for other kits. I've had to assemble the Filter Cap board and premount it in the set position to check for hole placement compatibility. Plopped a dab of RTV under each of the caps to stop them rattling round. The chassis is quite busy on both sides, so it's going to a sod, but not impossible.
* I assume placement of the eyelet board is about correct... i.e as about as far as pos from the PT?

While this post sounds grumbly, I am having fun. Grumpy fun! Any thoughts or tips always appreciated! :)


Image
Image
Attachments
MK-SR-WD.pdf
(116.17 KiB) Downloaded 114 times
MK-SR-SCH.pdf
(55.17 KiB) Downloaded 114 times

User avatar
Cdog
Vintage Post Junkie
Vintage Post Junkie
Posts: 4363
Joined: Wed Feb 07, 2007 3:01 pm
Location: Christchurch
Has liked: 3465 times
Been liked: 711 times

Re: Mojotone kit Super Reverb

Post by Cdog »

el byrdo wrote:Very cool man. Do you have any comments on your tweedish tourist pedal? I just bought it off trademe. Haven't tried it out yet as I have all my speakers out of my amps...
It's a lavache. Aint played through one in ages. Compares to Les Lius from memory

User avatar
Cdog
Vintage Post Junkie
Vintage Post Junkie
Posts: 4363
Joined: Wed Feb 07, 2007 3:01 pm
Location: Christchurch
Has liked: 3465 times
Been liked: 711 times

Re: Mojotone kit Super Reverb

Post by Cdog »

A long time coming... Progress pics! ♥

Image
Image
Image

Yoiks. There's still a lot of chassis left to fill! :shock:

Comments:
Took some time for me to figure out the back panel. Holes have changes, things have been moved.
No standby switch!
Fused all PT taps except Bias
MOV on IEC input
100nF filter across AC line, and a NTC Thermistor to soften the startup. Backup diodes to pre-rectify for the 5U4GB
Power tubes will be 5881
Installed a 3-way impedance switch for different speaker loads. The 50w OT does 2, 4 and 8 Ohms
Power-amp star ground has wandered out into the wilderness a little, hoping this wont be an issue
Little pcb on the dual pot is will be a Trainwreck 2 MV, it replaces the 220k grid leak resistors. The onboard resistors are for safety, pot wiper fail-safes... this mod is from Rob Robinette's excellent site.
Decided to build stock first then rewire in the MV after its work... because that's a much better idea! :roll: :thumbup:

User avatar
GrantB
ADMIN
Posts: 15843
Joined: Fri Oct 31, 2003 9:04 am
Location: Where I need to be
Has liked: 1353 times
Been liked: 2087 times

Re: Mojotone kit Super Reverb

Post by GrantB »

Tidy work!
"Man is the most insane species. He worships an invisible god and destroys a visible nature. Unaware that this nature he's destroying is this god he's worshipping." - Hubert Reeves

User avatar
Jay
Vintage Post Junkie
Vintage Post Junkie
Posts: 7761
Joined: Sat Sep 25, 2010 9:35 pm
Has liked: 1630 times
Been liked: 1297 times

Re: Mojotone kit Super Reverb

Post by Jay »

Nice work there. Same approach for me, LarMar MV to be tried once everything is sorted.
When faced with quality, I recognise it every time.

User avatar
Cdog
Vintage Post Junkie
Vintage Post Junkie
Posts: 4363
Joined: Wed Feb 07, 2007 3:01 pm
Location: Christchurch
Has liked: 3465 times
Been liked: 711 times

Re: Mojotone kit Super Reverb

Post by Cdog »

Alrighty... this has gone on long enough.

No thanks to an ongoing back injury I've had very little time for fun things over the last 10 Months. There was one final hiccup at boxing up-time... the chassis mounting holes in the head-cab were in the wrong place! :lol: Mojotone have been good about it, and quick respond... we reached a solution. No points lost as far as I'm concerned, overall it was a great quality amp kit :thumbup:


Image
Image
Image
Image
Image

Preamp tubes are a mix of TungSol and JAN. Power tubes are TungSol 5881s, the rectifier is a 5AR4, no standby switch, added a Master Volume but otherwise it's a reasonably stock AB763 Super Reverb circuit. It sounds absolutely outstanding. The reverb is drippy and cavernous, the Vibrato is pretty decent. Master Volume was well worth doing. Cab (a repurposed Spider-Valve) has 2x 10" 4-Ohm Jensen Alnicos, wired in parallel for 2 Ohms, the same impedance as the original 4x10 to match the NFB.

There's still some finishing touches to do, especially on the speaker cab, but she flies for now and I'm very happy to be playing this thing. Think I'm gonna need a compressor pedal haha

User avatar
kdawg2a
Vintage Post Junkie
Vintage Post Junkie
Posts: 3361
Joined: Sat Jan 16, 2010 7:28 pm
Location: U S and A
Has liked: 238 times
Been liked: 1040 times

Re: Mojotone kit Super Reverb

Post by kdawg2a »

GEARFEST!!!!
1935 Martin D-45, 1942 Gibson Southern Jumbo,1950 Fender Broadcaster, 1954 Fender Strat, 1958 Gibson Moderne prototype, 1959 Gibson Les Paul Standard.
1958 Fender twin, 1965 Vox AC30, 1966 Marshall JTM 45, 1977 Dumble OD Special.
Big black garbage bag full of original Klon Centaurs and TS808s.

User avatar
kdawg2a
Vintage Post Junkie
Vintage Post Junkie
Posts: 3361
Joined: Sat Jan 16, 2010 7:28 pm
Location: U S and A
Has liked: 238 times
Been liked: 1040 times

Re: Mojotone kit Super Reverb

Post by kdawg2a »

Corey, what is the speaker ohm output of this amp?

Edit: just seen it, 2 ohms. Bugger. I would have liked to try my 2x10 Weber 16 ohm cab on it!
1935 Martin D-45, 1942 Gibson Southern Jumbo,1950 Fender Broadcaster, 1954 Fender Strat, 1958 Gibson Moderne prototype, 1959 Gibson Les Paul Standard.
1958 Fender twin, 1965 Vox AC30, 1966 Marshall JTM 45, 1977 Dumble OD Special.
Big black garbage bag full of original Klon Centaurs and TS808s.

Post Reply