NAD - Marshall JCM600

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JohnnyC

JohnnyC

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so i had some spare cash that ive been looking for a 2nd amp to replace the Laney GH50L and blackstar HT-5 i recently sold.
i was looking at getting a blackstar HT20...but couldnt find one locally...then a few 2nd hand amps came up that caught my eye...namely a fender hot rod deluxe, Vox AC30 (the HRD was in bad condition and the AC30 sold before i got there)
then this came up

JCM600.jpg

JCM600stack.jpg


bought it off this was really cool old dude who had it in his studio for 8 years and its literally still has the new amp smell!!!
mint condition and recently retubed and serviced and sounds freaking great.

now i cant wait to fool people into thinking ive got a Marshall MG/Valvestate and trick them that i have super tone in my fingers.
 
damn that is one sleeper tone rig you've got there, happy NAD :rock:
 
had one myself & IMO was a marshall "scam"

open it up and look at the pc board it'll say "JTM60"


Marshall obviously had problems selling all the JTM60's (ie Famous for overheating problem due to the Board mounted Power Tubes and no ventilation !) they produced so they repackaged the JTM60 series as the "New JCM600"

every JTM60 & JCM600 Combo's I've seen had signs of the Power Tube pc board "warping" due to overheating - not a good thing !

I'm not trying to bash your new amp - just wanted to make you aware that the JTM/JCM60's do have an inherent design flaw which over time could result in damage to the transformers

does your head have the "small" output tranny (in comparsion to the typical Marshall output tranny's that are fairly BIG) ?

if so, I'll bet that the amp runs "hot" which leads to the overheating problem !

by "hot" I mean you'll feel it - the headshell will be very warm if not hot to the touch after 45-60 minutes of playing
 
Simple fix then. Make a homemade shell that has better ventilation. I assume the tubes hang down? That sucks, otherwise you could just take the chassis out and leave it around, that's what I used to do.
 
Somebody hook this gentleman up with an internal fan schematic!
Happy nad!
At least go get a lil clip on fan.... custom Soldano style headshell? :rock:
 
ive read about the problems about these amps RE overheating. but it seems most of them were to do with the combos?
i didnt read many problems RE the head version.

plus i actually jammed with a guy about 10 years ago who had one. he hasnt had any problems either.

for the price i took the risk. the guy had it recently retubed and serviced so meh. loving it so far.
 
JohnnyC":3arndghs said:
ive read about the problems about these amps RE overheating. but it seems most of them were to do with the combos?
i didnt read many problems RE the head version.

plus i actually jammed with a guy about 10 years ago who had one. he hasnt had any problems either.

for the price i took the risk. the guy had it recently retubed and serviced so meh. loving it so far.
Click to expand...

I like to throw that info out there just in case someone was unaware of the possible pitfalls of these amps & end up with a several hundred dollar "doorstop"

its still a marshall though so :rock:

fwiw, bet the JCM600 preamp running into a JCM800 power section would kick some serious ass :thumbsup:
 
^ was yours the head or combo version?

and design flaws aside...did you actually have any issues with your amp over the period you had it?
 
FuzzBoat...i think you cursed me.

amp wouldnt come off standby this morning...when it was perfectly fine last night!

didnt really feel like opening up amps on my sick day off work...looks like one of the fuses has blown.

fingers crossed that thats the only thing wrong.
 
ConcreteVampire":wokx014k said:
Somebody hook this gentleman up with an internal fan schematic!
Happy nad!
At least go get a lil clip on fan.... custom Soldano style headshell? :rock:
Click to expand...

:thumbsup:
 
This was my first amp! I remember it had a great tone...very unique but mine also unfortunately suffered from overheating.
 
well...i replaced the HT fuse (500ma) and the amp worked fine for 1hour+
after turning it off...it wont produce sound off standby. same fuse blown.

bugger.

i replaced the fuse with teh same value...but im not too sure if the original .was fast blow or slow blow.
im pretty sure the ones i purchased were fast blow.

i was really enjoying this amp as well.
 
JohnnyC":wnbpeeyt said:
well...i replaced the HT fuse (500ma) and the amp worked fine for 1hour+
after turning it off...it wont produce sound off standby. same fuse blown.

bugger.

i replaced the fuse with teh same value...but im not too sure if the original .was fast blow or slow blow.
im pretty sure the ones i purchased were fast blow.

i was really enjoying this amp as well.
Click to expand...


hey man

sorry to hear about the problem already !

hopefully its just a power tube that went bad and shorted out on you (the 2nd most likey culprit is a filter cap went bad)

if its blowing fuses the moment you take the amp off standby - You Have a Direct Short to Ground !!

So don't use the amp unless you want to be replacing Power & OutPut Transformers :doh:

If it turns out to be just a bad power tube be certain whoever works on the amp checks and/or replaces the screen resistors

when a power tube goes bad those screen resistors will heatup to the point where they get burnt
 
JohnnyC":173scwx3 said:
^ was yours the head or combo version?

and design flaws aside...did you actually have any issues with your amp over the period you had it?
Click to expand...

both were combo's


had to replace a couple "leaky" cathode caps in the preamp on the JCM600 combo - you could see the "white" substrate protuding from the tops !
 
amp is with a tech i trust atm...hes confirmed its blowing fuses but thats all i got out of him.

on another note...i manged to pick up a mint/used marshall 1936 cab...so hopefully the 600 will be sorted out soon so i can run a stereo/wet/dry rig with my framus.
 
problem was the problem was faulty at the PCB where the rectifier diodes were soldered....it was shorting by a hair's whisker andthe diodes where not fitted/soldered properly....
 
the amo is RAWKING now!!!

and with the 1936 cab its sounds...umm...very...marshally :rock:

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