Marshall Pcb Replacement And Tubes

[devilRED]

Last week bought a PCB for my Marshall DSL and 4 new JJ's EL34 everybody talks great stuff about the tone of this tubes,

After replacing the PCB i inserted the 4 new JJEL34 matched set, and when i plugged my JCM 2000 DSL for a bias adjustment, i hear a litlle crackle and after sometime it stoped, i adjusted the Bias, and all seemed fine.

Plugged my guitar and the tone was great and after 30 minutes i started to smell somthing burning, i looked the tubes and noticed that tow were red plating ... i had some Groove Tubes and inserted them, no crackle, adjusted Bias and and still working great, so my thought's are that those tow JJs had some defect ...

I adjusted the Bias a lot more low than the recomended by Marshall 75mV instead 90mV

Now look at what happens when i do a chord, the value goes up to 100mV, is this normal?

The logo of the JJs got grey after the red plated effect, i think i was lucky not to have damaged my amp ...

After making a research about red plating tubes, i found out many were JJs ... The tone was great no doubt about it, but i think quallity control is not good at JJs factory ...



Here is a vid i made with the Groove Tubes already inserted, pls don't quote tone and playing, i was filming at the same time



Here are how they ended up after the red plating

 

[ampmadscientist]

There is probably nothing wrong w/ JJ tubes...
and you still have some defect in the amp.

The information you provided...proves absolutely nothing...and is based purely on guessing and assumptions.

Inexperienced (who have no test equipment and no ability to diagnose a problem) will RUSH to blame the tubes.
Because it's easy and convenient....but also completely erroneous.

It is easy to blame problems on the tubes...but.....experienced people will know better.

99% of problems blamed on the tubes...turned out to be an entirely different problem.

It is possible that the circuit board you installed is defective...or it's wired wrong.
It is also possible that you have a defective speaker cable or the wrong impedance speaker.

AND this is a FACT:
We have had (rarely) defect tubes....but just as many defect Groove Tubes, as any others.

 

[devilRED]

Wouldn't the problema and the crackle persist even after i replaced the tubes?
Tryed other thing before instaling the Groove Tubes, inserted 1 good JJ on one side and the other on the other side, putting the amp working at 50 watts and connected from 8ohms to 16 has a safe mismatched and worked fine with those tow JJ.

Im not an amp tech, but i work on maintenance and iam used to replace PCB boards making electrical Connections etc
Tooked picture before disconnect and marked wires

 

[charveldan]

Your volume should be @ 0.00 [off] when biasing an amp.

My friend had a tube problem yesterday he brought over a Reason SM-50 amp it had all JJ's.
One of the power tubes were shooting sparks, & the preamp tubes were microphonic.

I pulled out all those piece of shit tubes and and replaced with ones i had here.

My advice is get rid of JJ electronic devices.

You set the tube bias @ idle, DO NOT PLAY THRU AN AMP WHILE BIASING.

 

[devilRED]

Your volume should be @ 0.00 [off] when biasing an amp.

My friend had a tube problem yesterday he brought over a Reason SM-50 amp it had all JJ's.
One of the power tubes were shooting sparks, & the preamp tubes were microphonic.

I pulled out all those piece of shit tubes and and replaced with ones i had here.

My advice is get rid of JJ electronic devices.

You set the tube bias @ idle, DO NOT PLAY THRU AN AMP WHILE BIASING.

That was just to see if the value raised or not with time and playing, i biased it at 0 volume but i never thought that the value would go up with the playing and the increase of gain ...

One thing must be true, you pay for you get, no wonder 4 JJ costed me 66€ and 4 Groove Tubes 174€, with JJs might be a question o luck ...

 

[Matt_Krush]

The J&J KT77's my JVM 410 are going on 2 years and haven't had any issues.

I am not saying that you didn't get some bad ones..you may have, but I have had just a good (or bad) luck with J&J as any other current production.

 

[charveldan]

That was just to see if the value raised or not with time and playing, i biased it at 0 volume but i never thought that the value would go up with the playing and the increase of gain ...

One thing must be true, you pay for you get, no wonder 4 JJ costed me 66€ and 4 Groove Tubes 174€, with JJs might be a question o luck ...

http://www.ebay.com/itm/Tung-Sol-Fa...985552?hash=item258b11bd50:g:QUMAAOxyyFhTd85w

Trust me you want these Holmes... ^^^^^^^^^

 

[devilRED]

http://www.ebay.com/itm/Tung-Sol-Fa...985552?hash=item258b11bd50:g:QUMAAOxyyFhTd85w

Trust me you want these Holmes... ^^^^^^^^^

I always put a Tung Sol preamp tube in V1 position, need to try those out some day

 

[SG~GUY]

The J&J KT77's my JVM 410 are going on 2 years and haven't had any issues.

I am not saying that you didn't get some bad ones..you may have, but I have had just a good (or bad) luck with J&J as any other current production.

-MATT speaks the truth, THEY ALL FAIL, EVERY BRAND, & as high as 50%, sometimes a bad run and 100% are bad, buy your tubes throuy a Good TUBE RETAILER they test, then if it fails, they'll replace it,-(usually)-depends!!

-GROOVE TUBES- they don't make tubes, they are a contractor, then a retailer, ultimately a -MIDDLE MAN- stealing your $$$

-buy from a -TUBE VENDER- get the exact tubes a lot lower in $$$, Usually a better warranty as well

 

[RickyLee]

The 100mA your were seeing is normal. Depending on the volume level you could see much higher than that. That is telling you the tubes are working.

But as others mentioned, when setting the bias you should have all volume OFF.

 

[devilRED]

The 100mA your were seeing is normal. Depending on the volume level you could see much higher than that. That is telling you the tubes are working.

But as others mentioned, when setting the bias you should have all volume OFF.

I did that was just monitoring the behaver of the BIAS

 

[devilRED]

By the way i set it to 75mV Marshall says should be 90mV but i think i've read somewhere in this forum that 83mV are fine ...

 

[RickyLee]

You want to actually go off the plate voltage you are running and then figure 60% to 65% idle. But I am thinking your 75mV/mA should be just fine. I usually set mine around 70mA. I heard no difference using a higher bias idle, so I went colder to play it safe.

 

[devilRED]

You want to actually go off the plate voltage you are running and then figure 60% to 65% idle. But I am thinking your 75mV/mA should be just fine. I usually set mine around 70mA. I heard no difference using a higher bias idle, so I went colder to play it safe.

In fact i had biased the amp to 70mV/mA when the red plating of the JJs occured, i went a bith higher with the Groove Tubes it has now

 

[mickeydg5]

JJ E34L are good and truth be told any tube out of the box can go bad early. It is called infant mortality of electronics devices or components.

Everything else is sounding good in the thread.

 

[SG~GUY]

JJ E34L are good and truth be told any tube out of the box can go bad early. It is called infant mortality of electronics devices or components.

Everything else is sounding good in the thread.

--(I.M.E.D.)--just like--(S.I.D.S.)--

--&--

--mothers against drunk drivers-(M.A.D.D.)--

--but I'm a member of a little known group-- ---(D.A.M.M.)--
--DRUNKS AGAINST MADD MOTHERS--

 

[charveldan]

By the way i set it to 75mV Marshall says should be 90mV but i think i've read somewhere in this forum that 83mV are fine ...

I set mine around 80 its not a problem.

 

[neikeel]

There are too many unknowns in this thread to comment firmly - last DSL that I had in had taken out two screen resistors, but they will be new on your board.
Generally I find JJ as good as any others, the set of KT77s in my DR103 that my son hammered for 18 months lost a tube but the rest were still in spec.
I agree that if you want to avoid the infant mortality issue you pay a little extra for a set of burned in then matched and tested from a reputable seller.
In the U.K. I use Hotrox or (if they have a special offer) Watford valves. You have loads of choice in the US.