2204 clone gut job
- Thread starter fitz
- Start date
PelliX
Well-Known Member
Be very careful to discharge electrolytics before testing them on there, those testers are surprisingly good often but they can't handle even relatively small residual charges. That cap measures fine, but just be aware that it tests them at ~5V instead of the 50V rating so there *may* be false positive readings for DC leakage, etc. There's no harm in reusing the components if they check out, but it's also the best moment to put in new parts if you feel so inclined, your call...
OP
fitz
Ambassador of DIY
So I have a question about the 22nF (0.022uF) capacitors.
Mojotone specs 630v and Amplified Parts has a few brand options like Mallory, Vishay (ERO) & Illinois.
But what about something like the "legendary" Zoso caps that are 500v?
My Hammond PT has an output voltage around 440v.
PelliX
Well-Known Member
Is that the AC peak voltage, AC RMS or DC after rectification? If that's your DC HT then 500V would be sufficient, though I'd be tempted to go with a higher spec for more tolerance. It would be fine either way though.
OP
fitz
Ambassador of DIY
Yeah, those other ones are about 1/3 of the price.
CoyotesGator
Ambassador of Reptilian Rum Bar Affairs
I can not remember ever having an issue with all of the Mallory caps I have installed.
OP
fitz
Ambassador of DIY
This 680nF (.68uF) cap & parallel 2k7 1w resistor from V1 pin 3 to ground is spec's as 150v on the Mojotone parts list.
The TAD branded cap that came with the amp says 680nF 150v.
I can't find an exact match from what's available on Amplified Parts.
The wiring diagram has 1.3v as the expected voltage at the turret connection from V1.
- How important is the 150v spec?
The only available Mallory .68uf is 100v. ($3.95)
I have a Vishay 250v in my list ($2.55), and there's also a 400v Vishay ($5.95).
Or a Zoso 200v ($11.40)
I had put all Vishay 22nF coupling caps in my list because of this cap.
Just so they all match brand - I know it doesn't matter...
If the 100v Mallory is sufficient, I could also go with all Mallory caps.
PelliX
Well-Known Member
Not important, or better said; it's massively over spec'd. 100V would be sufficient. While fairly inconsequential it would be best to orient this cap correctly, i.e. the outer foil side to ground. Some caps are marked (Mallory I believe can be trusted in this regard), others aren't and some are even labeled reversed. If you have a scope it's easy to test - alternately clip each end of the cap to the scope and leave the other floating. The side with the biggest "noise" deflection on screen is the outer foil end.
Not very important for this position, but worth getting right if you're re-doing it anyway. Particularly for coupling caps this is more important.
syscokid
Ambassador of War & Peace
Yes you have…
… And you have gone deep too. Might as well go deeper!
For Marshall builds, I’m quite satisfied with the modern Mallory 150’s. Even more satisfied with the Vishay MKT-1813’s, which happen to have a smaller profile compared to others.
XTRXTR
Well-Known Member
Looking forward to your build @fitz
I know I'm late butt my 2¢
I like the Illinois Yellow 630V Polyprops for the 22nF couplers they are cheaper and never heard a difference. that 680nF can be as low as 25V, it is only on the cathode which will develop about 2VDC to 3VDC if you are building to stock. Marshall has it around 1.9VDC, MHuss has it at 2.24V measured at Idle 120VAC mains.
this following is just XTR info:
Personally I use an LED there per Valve Wizard. Actually mine is a three way switch two LEDs and the standard 680nF with the resistor.
An LED while active acts like a large capacitor between its cathode and anode allowing all frequencies and allows max plate output with very low Z at the same time. You don't need the resistor with the LED. So you can get all the low and high signal your guitar signal can produce amplified into the next stage for a few cents. The Cathode VDC=LED Vf. By using a switch I can voice a very clean cold bias, an original 2204 Marshall, or hot bias for great even harmonics. Different LED colors give different Cathode bias from about 1.2VDC to about 3VDC.
Of course I only do this on my own chassis designs, I would never drill a hole into an original Marshal JMP or JCM800.
Why would you want this?
This allows Single coil and Humbucker guitar tone to be voiced quickly and still have the rest of the Tone stack and effects for whatever other tweaks you want. Its a mod that allows multiple voicings from one amp.
I know I'm late butt my 2¢
I like the Illinois Yellow 630V Polyprops for the 22nF couplers they are cheaper and never heard a difference. that 680nF can be as low as 25V, it is only on the cathode which will develop about 2VDC to 3VDC if you are building to stock. Marshall has it around 1.9VDC, MHuss has it at 2.24V measured at Idle 120VAC mains.
this following is just XTR info:
Personally I use an LED there per Valve Wizard. Actually mine is a three way switch two LEDs and the standard 680nF with the resistor.
An LED while active acts like a large capacitor between its cathode and anode allowing all frequencies and allows max plate output with very low Z at the same time. You don't need the resistor with the LED. So you can get all the low and high signal your guitar signal can produce amplified into the next stage for a few cents. The Cathode VDC=LED Vf. By using a switch I can voice a very clean cold bias, an original 2204 Marshall, or hot bias for great even harmonics. Different LED colors give different Cathode bias from about 1.2VDC to about 3VDC.
Of course I only do this on my own chassis designs, I would never drill a hole into an original Marshal JMP or JCM800.
Why would you want this?
This allows Single coil and Humbucker guitar tone to be voiced quickly and still have the rest of the Tone stack and effects for whatever other tweaks you want. Its a mod that allows multiple voicings from one amp.
67plexi
Ambassador of Amps
50v is more than enough my 1968 super lead 100 has a 6.4v stock the voltage is under 2 voltsThis 680nF (.68uF) cap & parallel 2k7 1w resistor from V1 pin 3 to ground is spec's as 150v on the Mojotone parts list.
The TAD branded cap that came with the amp says 680nF 150v.
I can't find an exact match from what's available on Amplified Parts.
The wiring diagram has 1.3v as the expected voltage at the turret connection from V1.
I'm assuming if it actually sees 150v, that would be bad...
- How important is the 150v spec?
View attachment 111225
The only available Mallory .68uf is 100v. ($3.95)
I have a Vishay 250v in my list ($2.55), and there's also a 400v Vishay ($5.95).
Or a Zoso 200v ($11.40)
I had put all Vishay 22nF coupling caps in my list because of this cap.
Just so they all match brand - I know it doesn't matter...
If the 100v Mallory is sufficient, I could also go with all Mallory caps.
OP
fitz
Ambassador of DIY
Parts package arrived today.
Looks like I got everything on the list except the free stickers.
Going to start with replacing the turret that fell out while cleaning the board - and adding a few for the EL34/6550 switching.
Then I can move on to repopulating the board and replacing the chassis mounted stuff.
I put new fuse holders and tube sockets on the list as well as all new pots.
That stuff all looked re-used before I even relocated everything to the new chassis.
Had the 10uF Sprague axial caps and 2 of the big F&T 50/50 can caps from an unused set, so just added the 3rd F&T.
Those Malory coupling caps are quite a bit smaller than the TAD ones that were there before.
The old circuit had a lot of 2w resistors where 1w is spec'd, so hopefully everything will be easier to position and work with.
Looks like I got everything on the list except the free stickers.
Going to start with replacing the turret that fell out while cleaning the board - and adding a few for the EL34/6550 switching.
Then I can move on to repopulating the board and replacing the chassis mounted stuff.
I put new fuse holders and tube sockets on the list as well as all new pots.
That stuff all looked re-used before I even relocated everything to the new chassis.
Had the 10uF Sprague axial caps and 2 of the big F&T 50/50 can caps from an unused set, so just added the 3rd F&T.
Those Malory coupling caps are quite a bit smaller than the TAD ones that were there before.
The old circuit had a lot of 2w resistors where 1w is spec'd, so hopefully everything will be easier to position and work with.
Frodebro
Well-Known Member
Far Rider
Ambassador Of The Cataverse
Get yer mind out of the gutter
Frodebro
Well-Known Member
Get yer mind out of the gutter
I have absolutely no idea what you're talking about...
paul-e-mann
Member
Since you're buying all new parts, buy another chassis for the old parts and put it back together, now you got 2 and sell one!
OP
fitz
Ambassador of DIY
Building something usable from the discarded parts would entail a bit more than reassembly.
Most of the stuff that I just bought for the rebuild aren't the expensive parts of an amp.
I'd need some iron, and a circuit board for starters.
I'm also reusing the power / standby switches, knobs, impedance selector and power cord jack.
Add in another chassis and face plates too, and I might as well just get a whole new kit.
I was just thinking of keeping the discards for spares, but if anyone is interested any of the little stuff, let me know.
OP
fitz
Ambassador of DIY
Here's a nice 2204 starter kit if anyone is interested...
It even comes with a few extra parts.
It even comes with a few extra parts.