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Post by splawndude on Feb 12, 2018 22:35:40 GMT -5
Speaking of tubes... So I go to plug into my Rectoverb today and there is no sound. I had just been in there a few days ago but there is no sound now. First thing I do? Unplug from my complex board with the A/B box and plug straight into the amp. Nothing. Neither channel. I'm like WTF? Tubes are are lit up as normal. Nothing has been moved around it just sits there day in and day out. Well, I DO know that one of our cats likes to mingle around back there behind the chaos so maybe she pulled the speaker cable out. IKES. Nope, speaker cable along with all the other cables are intact. So I crank up the amp to what normally would be deafening and I hear some slight distortion on the OD channel as I chug on some open strings. So I start to tap on all the tubes with a pencil starting with the power tubes. As I carefully listen for anything at all coming out of the speaker cabinet I work my way down the line from V5 to V1. As soon as I tap on V1... BINGO Microphonic preamp tube. I put a spare Chinese 12AX7-XC or something something in there and BOOM. Amp is back  |
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Post by briman on Feb 13, 2018 0:00:45 GMT -5
Speaking of tubes... So I go to plug into my Rectoverb today and there is no sound. I had just been in there a few days ago but there is no sound now. First thing I do? Unplug from my complex board with the A/B box and plug straight into the amp. Nothing. Neither channel. I'm like WTF? Tubes are are lit up as normal. Nothing has been moved around it just sits there day in and day out. Well, I DO know that one of our cats likes to mingle around back there behind the chaos so maybe she pulled the speaker cable out. IKES. Nope, speaker cable along with all the other cables are intact. So I crank up the amp to what normally would be deafening and I hear some slight distortion on the OD channel as I chug on some open strings. So I start to tap on all the tubes with a pencil starting with the power tubes. As I carefully listen for anything at all coming out of the speaker cabinet I work my way down the line from V5 to V1. As soon as I tap on V1... BINGO Microphonic preamp tube. I put a spare Chinese 12AX7-XC or something something in there and BOOM. Amp is back I have never had this happen to me and i am wondering why? I usually change my pre amp tubes every 2nd power tube change but sometimes every power tube change. So maybe it only happens to pre amp tubes that have been used for quite a long time? (4 + years) How old was your pre amp tube splawndude? |
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Post by gtrjunior on Feb 13, 2018 6:51:19 GMT -5
Glad it was a simple fix! briman....I don’t change preamp tubes until they fail. And so far I’ve never had that happen. Preamp tubes can and often last years....I’m talking decades. They don’t take the same type of heat punishment that power tubes do. The only time I swap preamp tubes is when I’m looking for a tonal difference. |
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Post by briman on Feb 13, 2018 10:18:57 GMT -5
Hmmm so i have wasted alot of money and tubes lol
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Post by gtrjunior on Feb 13, 2018 10:42:47 GMT -5
The preamp tubes in my 2204 are 50 years old....from the 60’s
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Post by briman on Feb 13, 2018 14:02:57 GMT -5
Wow! I didn't know you had a JMP? How do you like it compared to your QR?
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Post by gtrjunior on Feb 13, 2018 14:12:39 GMT -5
It’s a JCM 800. The 50w are model #2204.
If I’m not mistaken it’s the same or very similar circuit. The JMP had a plexi style headshell. And at some point in the early 80’s (‘81?) they switched shell styles. Mine is from 1986.
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Post by splawndude on Feb 13, 2018 23:11:51 GMT -5
brimain - yeah, you don't need to replace them that often. Only when they die or go microphonic. I have a video of how to test for microphonic tubes if you are interested. My next goal is to get some NOS (New Old Stock) preamp tubes of all kinds. Telefunken. RCA. Phillips. Tungsram. Mullard. etc. The preamp tubes in my 2204 are 50 years old....from the 60’s Yep. You know the old saying. They don't make 'em like they used to. |
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Post by briman on Feb 14, 2018 13:18:29 GMT -5
Thanks guys.......i will hold onto changing preamp tubes a little longer now lol.
The JCM 800 2204 is a very highly regarded Marshall which is often compared to the legendary 2203 but the 2204 has the clean chanel.
Gtrjunior, after playing each of them, what are your thoughts? I am curious about differences when playing lead in particular. I have owned JVM's and DSL's and a JCM900 but never tried an 800.
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Post by gtrjunior on Feb 14, 2018 13:28:21 GMT -5
Thanks guys.......i will hold onto changing preamp tubes a little longer now lol. The JCM 800 2204 is a very highly regarded Marshall which is often compared to the legendary 2203 but the 2204 has the clean chanel. Gtrjunior, after playing each of them, what are your thoughts? I am curious about differences when playing lead in particular. I have owned JVM's and DSL's and a JCM900 but never tried an 800. No, you’re thinking if the 2205. The 2203/2204 are both single channel 100/50 waters and are all tube circuits. The 2210/2205 are dual channel 100/50 watters and use diode clipping in addition to the tube gain. They are capable of more gain than the 2203/2204 models. They were popular but not as popular as the all tube versions....you know, the purist guitar player philosophy. Lol plus there was bleed through on the clean channel. You could faintly hear the overdrive bleeding through to the clean channel. It was fixable but still. I like the amp a lot. I’ll never sell it but it can’t do what the Quickrod does. Not without a boost or some sort of preamp. On its own it’s a classic rock amp....similar to early Whitesnake. However I’m sure his was either modded for more gain or boosted with a TS or other pedal. With a boost it’s capable of a lot of musical ground. |
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Post by gtrjunior on Feb 14, 2018 13:35:52 GMT -5
 Don’t mind the ugly pink carpet! It was there when we bought the house. We pulled it up...the house has hardwoods through the first floor. |
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Post by briman on Feb 14, 2018 16:37:57 GMT -5
Nice set up and nice Lesters!!
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Post by gtrjunior on Feb 14, 2018 18:11:55 GMT -5
Thanks! That’s actually a really old pic from about 5-6 years ago. One of these days I’ll update the family photo.
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Post by splawndude on Feb 14, 2018 23:02:35 GMT -5
YUM
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