Vietnamese Marshall
Phil Allison
** A rather new looking Marshall " MA100H " valve head landed on my bench
today - but it looked a bit different. On the back it says " Made in Vietnam
" - so this is the first non UK made ( ie assembled) Marshall, at least
that I have ever seen.
The amp was silent, valves all lit up but no output whatsoever and no extra
current draw when the Standby switch was closed. OK - so where is the damn
HT fuse ? Nothing on the back so it must be inside - another first for a
Marshall valve amp. On the PCB is a 630mA delay fuse - very blown -
fitting a new one got the amp running. The fuse was original and as marked
on the PCB.
Bit of poking about finds that both 1/4 inch QCs on the PCB used for output
valve grid drive are very loose - easy fixed. But was this the cause of
fuse blowing? Nope.
That 630 mA HT fuse should be 1 amp at least, since it is fitted in the
secondary of the PT. On test, the fuse had to pass just over 1 amp rms when
the amp is over-driven. The primary AC current draw is 2 amps rms at the
same time ( ie 480VA). The amp has a 1 amp delay fuse now.
On sine wave test, there is significant crossover distortion on the CRO
screen at 1/2 output and above. The bias setting seemed OK - there are two
trims inside and a pair of 1 ohm resistors in each pair of output valve
cathodes.
On checking the screen B+ supply, the cause is simple. There is no filter
choke of course ( what are they ?) and instead a 470 ohm ,7W resistor. So
the screen B+ supply falls like a rock soon as the amp is driven. Guess
this helps the crappy Chinese EL34s to survive overdriving.
Besides the above bad points, there are lots more.
The AC tranny is undersized - it looks like a 250VA type and needs to be
400VA to withstand hard use in this amp. Even sitting on the bench with a
605mA idle current from the AC supply, the internal temp rise is almost 40
degrees C. A couple of hours of heavy metal on a warm night will see it off.
The same * ridiculously fragile* plastic shaft pots as used on other recent
Marshalls have been fitted - one light bump on the knob = nasty
intermittent fault.
There is no AC voltage selector fitted and no internal option either,
another first in a Marshall valve head. All the fasteners are metric too,
not one single concession in sight to the brand's UK origin.
There ARE two small screw-in bulbs ( labelled 12V ) fitted inside the
cabinet that illuminate the whole chassis and the "Marshall" logo through
the open weave cloth. These are not ordinary 12 volt dial lamps but special
dual, orange LEDs - one chip connected for each polarity when fed with AC.
Next the these is a non Accutronics ( Belton ?) reverb tank.
All the jack sockets ( 7 of them ) are very fragile, PCB mount types.
Every single part in the amp looks like it came either from China, Korea or
Taiwan and then assembled in Vietnam.
Good points:
--------------
The 4 x EL34 output valves and the 12AX7 PI are on ceramic sockets, hand
wired to the two trannys and the PCB.
The main PCB looks like it is easy to get lose and invert for servicing.
The amp is pretty cheap to buy.
But a used example from the 1980s is a way better product, full of UK made
transformers and other parts that have proved their ability to survive in a
Marshall.
BTW:
There seems to be no schematic available on the net.
.... Phil
White Spirit
I was wondering what the construction of their cut-price valve amplifier
range would be like. It doesn't inspire me to try one.
I think I'll stick with their Milton Keynes production. Since I got the
bad soldering fixed in my JCM2000, it has taken a lot of heavy usage
with no problems. I am very careful with the PCB-mounted valve sockets,
however...
Lord Valve
Belton bought Accutronics awhile back.
All the currently produced tanks which are
badged "Accutronics" are made in Korea.
Phil Allison
"Lord Valve"
>
> Belton bought Accutronics awhile back.
>
> All the currently produced tanks which are
>badged "Accutronics" are made in Korea.
** That might explain the big dive in quality lately.
I have had to return new tanks to my supplier with open drive coils and get
a steady stream of units where the drive coil has failed cos of that STUPID
push on connector that bangs into the chassis.
But the one in the Vietnamese Marshall is black in colour and carries no
Accutronics markings or codes.
.... Phil
Phil Allison
"Phil Allison"
** Correction:
> But the one in the Vietnamese Marshall is black in colour and carries no
> Accutronics markings or codes.
** A white paper label carries the code " 3DB2C1D " which is not any
Accutronics number.
But that seems to be a mistake as the unit is clearly an " 8DB2C1D"
The maker is now called " Accu-Bell Sound Inc " of Seoul, Korea.
http://www.accutronicsreverb.com/
.... Phil
Mike Schway
Hi, Phil
I wouldn't let this be TOO much of a negative. The last decade of
made-in-USA Accutronics tanks have been absolutely HORRID. The
Beltons really do sound better (to my ears, at least).
OTOH, other stuff Marshall has been doing in this century is
unforgivable. My latest "favorite" (HAH!) is the master volume
control of the DSL 201 and 401. It's one of those cheesy square-body
pots with a long plastic D-shaft you've mentioned. The least bit of
side thrust will permanently send this pot into the "intermittent"
category. The problem with this (other than audible crackles when
it's turned) is that the pot serves double duty as a volume control
(of course) AND bias feed resistor pair (WTF???). If the wiper opens
up, guess what: the tubes run away. All this to save maybe $2 per
amp on a quad of 0.1uF caps and a pair of resistors.
--Mike
Phil Allison
"Mike Schway"
"Phil Allison"
>
> ** Correction:
>
> > But the one in the Vietnamese Marshall is black in colour and carries no
> > Accutronics markings or codes.
>
> ** A white paper label carries the code " 3DB2C1D " which is not any
> Accutronics number.
>
> But that seems to be a mistake as the unit is clearly an " 8DB2C1D"
>
> The maker is now called " Accu-Bell Sound Inc " of Seoul, Korea.
>
> http://www.accutronicsreverb.com/
>
> .... Phil
Hi, Phil
I wouldn't let this be TOO much of a negative. The last decade of
made-in-USA Accutronics tanks have been absolutely HORRID. The
Beltons really do sound better (to my ears, at least).
** The failure rate on Accutronics tanks is waaay high and almost entirely
due to one thing - that STUPID push-on plug on each drive coil assembly.
It strikes against the chassis and that breaks the fine wire in the coils.
IME - the long, 3 spring units sound best and are very like older Hammond
brand units.
If you want to make recent ones survive do three things:
1. Remove the plastic plugs and solder the leads to the 2 pins on the drive
units.
2. Add a piece of thin, stick-on felt to the middle of the tray under the
springs - say 3 inches by 2 inches or so.
3. Add rubber grommets to the two holes in the tray that act as a travel
limiters.
OTOH, other stuff Marshall has been doing in this century is
unforgivable. My latest "favorite" (HAH!) is the master volume
control of the DSL 201 and 401. It's one of those cheesy square-body
pots with a long plastic D-shaft you've mentioned. The least bit of
side thrust will permanently send this pot into the "intermittent"
category. The problem with this (other than audible crackles when
it's turned) is that the pot serves double duty as a volume control
(of course) AND bias feed resistor pair (WTF???). If the wiper opens
up, guess what: the tubes run away.
** That is 100% insane.
The design wankers at Marshall need shooting.
.... Phil
Gareth Magennis
"Phil Allison" <phi...@tpg.com.au> wrote in message
news:iplpsf$5d8$1...@news-01.bur.connect.com.au...
>
> "Mike Schway"
> "Phil Allison"
>>
>> ** Correction:
>>
>> > But the one in the Vietnamese Marshall is black in colour and carries
>> > no
>> > Accutronics markings or codes.
>>
>> ** A white paper label carries the code " 3DB2C1D " which is not any
>> Accutronics number.
>>
>> But that seems to be a mistake as the unit is clearly an " 8DB2C1D"
>>
>> The maker is now called " Accu-Bell Sound Inc " of Seoul, Korea.
>>
>> http://www.accutronicsreverb.com/
>>
>> .... Phil
Hmm, something up with this new Accutronics company it seems, Marshall
cannot get any supplies from them at present.
Gareth.