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Aha, I forgot that one was also in the picture :-) Anyway, I just installed a standard 120 Ohm 2W resistor, in addition to replacing the Zener-diode with a new one. It didn't make any noticable difference. It turned out that the Zener was not damaged (at least electrically), even though it...

If I remember correctly, my Express 5:25 head weighs around 11kg. I used one of those fish weights. Best regards, Torquil Sørensen

Got an answer from Mesa that the 39 Ohm 5W resistor in the original picture is definitely not from the factory. I have another one i parallel below, so it's 19.5 Ohm. The original resistor 120 Ohm 2W, and should be located under the board. It determines the tube bias in 5W mode, so this is...

Aha, if 0V shuts it down then it is natural that I get 0V on one of the tubes, since the amp is only supposed to use one tube in the 5W mode. And now I know which one it is :-) I only measured without the tubes, since that was sort of trivial to do. I'm quite careful when doing anything inside...

Hi, I'm in Oslo, Norway, so I found a local electronics store, and will get a few of those tomorrow. It will be interesting to see what happens when I put in a new one. Btw, I have no experience with the tube voltages, but I saw somewhere that they should not exceed around 300V for en EL84 tube...

Yes I agree. But I don't have any experience with such things so I couldn't say if this could is a result of something electrical or mechanical... Maybe it could happen if it got really hot. Anyway, I got an answer in an electronics forum where I also posted this picture. Apparently this is a...

Hi again, today I took one more look inside. When I looked underneath the card where the output jacks are connected, I noticed what looks like a broken diode located between the two 4 Ohms outputs. I don't have much practical experience in electronics, but this diode must have been through an...

Good idea, phyrexia. Just tried it, but unfortunately it made no difference at all. Btw, the tubes in it came from the previous owner, they are two JJ EL84 power tubes, and the preamp tubes are marked (going from V1 to V5) Elektro Harmonix, Ruby, then 3 x Mesa Russian. I will soon have a chance...

Sorry, I won't have access to my speaker cabinet for maybe a week or so, or even longer. But the most obvious sign that something is wrong in the 5W mode is the low volume. If I have the gain and master about halfway up, I get a volume similar to normal speech. It is still possible to...

Thanks. It's probably supposed to be there, since Don has it too. Then there must be some other reason for the faulty 5W mode. Hopefully it will just be the tubes...

Hi, I am going to make a footswitch for my Express 5:25. But I have a question as to how the original footswitch works (I don't have one): I am pretty sure that the reverb switch is completely independent of the channel switch, i.e. the reverb setting will not change as I change the channel...

Hi, I just bought a used Express 5:25 head which I really like, but there is something fishy about the 5W mode: the sound is much weaker than expected and with too little bass. The 30W mode is working fine. Then I had a look inside the amp, and noticed a difference compared to a picture in a...