Second Hand VH4 Tube/Fuse Fault & Transformer Hum

  • Thread starter Thread starter negativedan
  • Start date Start date
N

negativedan

New member
Hi guys,

New user here (with some mild lurking in the past) and proud new owner of a used VH4 blueface reissue! I did a lot of searching but couldn't find anything exactly what I'm experiencing so forgive me if this has been answered.

Anyways, here is what I'm experiencing. I received my amp a few days so of course my first instinct was to see what this thing can do. I get everything plugged in and throw it in standby. The first thing I noticed was a hum from the transformer, not sure if this an issue but a google search tells me it's nothing to worry about if it's not coming from the speakers. So I start playing around a bit and everything sounds good to me otherwise. Day 2 I turn it on and immediately hear some loud crackling through the speakers which I initially thought was my cable/guitar jack, this only happened for a couple seconds and played fine afterwards. Day 3 play for a quick 10 minute jam and on shutdown I hear the crackle through the speaker again (very brief) but then at the same time I notice my wall light up blue. I check behind the amp to see what that was and see 3 of the 4 power tube fault lights are on. I believe these may have been on the whole time and the fault led only got brighter/noticeable when the crackle occurred. Have only played at bedroom level so wasn't really pushing it if that matters.

Another issue that happened only once and may or may not be related, on Day 1 or 2, when switching from on to standby, channels 1-3 lit up and channel switching became unresponsive until i powered off and on again.

So, I want to conclude that the tubes must've been damaged on their long journey from CA to NY and caused them to short and blow the fuses. (new to tube amps as well so I didn't think to check this) I'm looking into buying a new set of tubes and fuses but my main questions/concerns are:

-Is it possible a damaged tube could have caused more damage that is not immediately visible/apparent, and if so what should I look out for, like any resistors or caps etc.
-Are tubes still supposed to glow once a fault is triggered?
-Could this be the cause of the transformer hum? If not, is this actually normal or is it generally supposed to be completely silent and is there another fix? I wouldn't say it's loud but definitely audible in a quiet room
-Lastly, looking for any thoughts on the channel freezing on going back into standby

This is basically my dream amp (right after an original blue) and want to keep it in tip top shape, I'm so excited to finally have a VH4 but now I'm a little scared to turn it on until I know it's safe lol. I also feel pretty comfortable tinkering if need be.

Any input would be greatly appreciated and thanks for your time!
 
After digging around a lot more today I think I answered at least a few of these things.
-It seems the only other easily damaged piece due to a tube short would be the hum trimmer so I'll have to test that, anyone know how to confirm that's working properly?
-I learned it is normal for the tubes to glow with the fault light active. However is it normal for the led to 'intensify' or pulse? I noticed during one of the crackles that the led became much brighter and then died down
-The transformer hum won't be determined until new tubes are installed but probably normal. Would still like to know what's considered a normal noise level as I know that can be a little subjective
-Without being able to do more testing, I think I'm going to attribute the channel freezing to the bad tubes as well but will also be determined once the new ones are installed.

I have 4x JJ KT77s, 2x Ruby 12AX7AC5 HG+ and 5x Ruby 12AX7AC5 HG on the way along with a bunch of ceramic slo-blo 250mA fuses

I'll keep this thread updated as well in case it ever becomes useful for anyone
 
Ok back for the update and to talk to myself one last time lol. I replaced all tubes and fuses and biased the amp according to the service manual. There was one yellow wire connecting a tube pair to the board that came loose just by breathing on it so I resoldered that bad boy in there good. Was thinking that may have been the cause of the crackling if not the tubes. Either way, haven't heard it return in a couple sessions. The transformer hum is still present, even tightened them down slightly. Also bought a high end power cable and conditioner but seemed to not have any effect. Guess that's just normal operation or something I'll have to live with. Didn't have to test the hum trimmer as apparently it isn't present in my amp and seems to have been replaced by two resistors. Lastly I'm going to assume the varying fault led intensity is normal and nothing to worry about anymore anyway
 
I’m really not a tech , just a hack ..
The amp must have had a bad tube at one point that de soldered the wire.
May be a good idea to check the screen resistors to see that they are working properly.
Also check the connections on the transformers.

Transformer hum could be your power?
My Herbert hums , VH4 does not. If your wires are good and amp sounds great, I wouldn’t worry too much about it.
 
Hey man thanks for the input! I actually didn't think to test the screen resistors but I'll check that out, visually they looked fine when I had her opened up though.

And yea I think the hum isn't too much to worry about just wanted to make sure it wasn't a red flag for something going wrong. I'm sure it's one of those 'your mileage may vary' or I just have crappy power in my house.
 
How are you liking it the amp now? Btw, if you ever want/need to sell it, I will buy it from you the second you want to let it go!
 
Back
Top