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This may be a dumb question....

JohnnyChatter

JohnnyChatter

Apr 23, 2011
1,424
1,786
Denver, Colorado
#1
I looked through the threads and can’t find an answer. I was shipped a Fender Bassman 300 Pro (not Super Bassman!!!) and the dude pulled the tubes out and packed them separately... does it matter what order I plug them back in or do I need to rebias. If this has been asked before just link me to the thread. Thanks!
 
#2
The order can make a difference. With some amps you wind up sorting the tubes a bit between the sockets to get the current passing through each tube as even as possible. This is because of variance between tubes and variances between the components in amp. In order to sort the tubes, some sort of bias probe is required to measure the current passing through each tube in the amp.

It is advisable to check the bias of the amp. Originally bias was set to 100mV at the test points per the manual, but I found a post from @tombowlus that Fender revised the bias down to 80mV.

For the bias and balance procedure, see page 8. https://www.fmicassets.com/Damroot/Original/10001/OM_leg_bassamp_Bassman_300300_PRO_20022013.pdf

Congrats on the amp.
 
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#5
Honestly, I think pulling the tubes when shipping is absolutely useless. I've shipped and had shipped a number of tube amps over the years, and all of them had the tubes inside and none of them have ever had a problem. Not saying you'll never have a problem, but if you can have a problem with the tubes being inside the amp, you can also have a problem with the tubes being shipped separately. That said, I wouldn't worry too much about which tube goes where. As long as you have the proper type of tube for each socket, you should likely be good to go.
 
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#7
JimmyM said:
Honestly, I think pulling the tubes when shipping is absolutely useless. I've shipped and had shipped a number of tube amps over the years, and all of them had the tubes inside and none of them have ever had a problem. Not saying you'll never have a problem, but if you can have a problem with the tubes being inside the amp, you can also have a problem with the tubes being shipped separately. That said, I wouldn't worry too much about which tube goes where. As long as you have the proper type of tube for each socket, you should likely be good to go.
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Yes. I put crumpled newspaper around the tubes to keep them stable in the socket and ship them in the amp.

Just make sure when you get a tube amp, make sure all the tubes are seated properly before you hit the power switch.
 
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#8
JohnnyChatter said:
Man I was afraid of that. Thanks for the info though! I’m not sure why they pulled the tubes and gave me no guide to what order they were in....
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If you have a multimeter, or know someone with a multimeter, I would install the tubes and bias the amp to 80mV. It's an easy process, just be careful to line of up the guide pin with the key in the tube socket. If the bias cannot be set to achieve 80mV, take the amp to a technician.

I have had the guide pins snap off a couple of tubes that were left installed. The amp was poorly packed and incurred other minor damage as well. Another thing that happens is a tube may come unseated and bounce around inside the amp. I have had this happen once and considered myself lucky that the tube's glass envelope did not get shattered. Incidence of damage is low, but I prefer for the output tubes to be numbered, removed, and packaged in bubble wrap.
 
#9
Wasnex said:
If you have a multimeter, or know someone with a multimeter, I would install the tubes and bias the amp to 80mV. It's an easy process, just be careful to line of up the guide pin with the key in the tube socket. If the bias cannot be set to achieve 80mV, take the amp to a technician.

I have had the guide pins snap off a couple of tubes that were left installed. The amp was poorly packed and incurred other minor damage as well. Another thing that happens is a tube may come unseated and bounce around inside the amp. I have had this happen once and considered myself lucky that the tube's glass envelope did not get shattered. Incidence of damage is low, but I prefer for the output tubes to be numbered, removed, and packaged in bubble wrap.
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Thanks for the info brother! I bought this head as a second to my original on a great eBay deal so I’ve biased the original before. I set it to 100 on my old one but I have heard of the 80mv was later recomended from a different thread. I’m just gonna put the tubes in today than bring my multimeter home from work later tonight. I need to grab a speaker cable also anyhow. 6 heads and 4 cabs in my living room and I can’t find a single speaker cable.... I haven’t had any problems before shipping heads with the tubes left in them but all of them had tube retainers minus my Marshall and when they packed that they opened it up and threw a ton of bubble wrap inside of it... good thing I noticed that before I turned it on. It’s probably best I check the bias anyhow when I get a new amp I suppose.
 
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#10
Nighttrain1127 said:
They pulled the tubes because there is less chance of them being damaged if they are out and protected. They are usually shipped in pairs or marked V1 V2 ect. Are you sure they did not write the tube location in the glass somewhere with a marker?
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No. I looked pretty hard. I was super careful and moved slowly because I didn’t want to miss or loose anything.
 
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#11
JohnnyChatter said:
Thanks for the info brother! I bought this head as a second to my original on a great eBay deal so I’ve biased the original before. I set it to 100 on my old one but I have heard of the 80mv was later recomended from a different thread. I’m just gonna put the tubes in today than bring my multimeter home from work later tonight. I need to grab a speaker cable also anyhow. 6 heads and 4 cabs in my living room and I can’t find a single speaker cable.... I haven’t had any problems before shipping heads with the tubes left in them but all of them had tube retainers minus my Marshall and when they packed that they opened it up and threw a ton of bubble wrap inside of it... good thing I noticed that before I turned it on. It’s probably best I check the bias anyhow when I get a new amp I suppose.
Click to expand...

IMHO, it's always a good idea to check the bias when you get an amp.

FYI, the tubes that snapped off the guide pins where held in place by clamp style retainers.
 
#12
Wasnex said:
IMHO, it's always a good idea to check the bias when you get an amp.

FYI, the tubes that snapped off the guide pins where held in place by clamp style retainers.
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Dang! That ups/fed ex dude must have really thrown that puppy around! I guess I could see the retainers not helping so much if the amp was on its side being that they push down. I’m tempted to just throw the GE’s out of the ampeg I’m selling with the groove tubes that came with the fender as long as I’m gonna be biasing amps.
 
#13
JohnnyChatter said:
Dang! That ups/fed ex dude must have really thrown that puppy around! I guess I could see the retainers not helping so much if the amp was on its side being that they push down. I’m tempted to just throw the GE’s out of the ampeg I’m selling with the groove tubes that came with the fender as long as I’m gonna be biasing amps.
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It was an Skunk SVT packaged in bubble wrap. The amp was face down and all the bubble were crushed by the weight of the amp. The mid range control was snapped off as well.

IMHO, if you didn't list the GEs as part of the sale, setup the amp with the GTs.
 
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#14
I usually pull the power tubes and wrap them in bubble wrap and put them inside the amp. Not saying it actually prevents mishaps but I bought a V4B from someone on the west coast with Supposedly the original tubes in it . When it arrived the shipping box looked fine but 3 of the tubes were Milky white. Immediate retube and the seller paid no problem.
 
#15
JimmyM said:
Honestly, I think pulling the tubes when shipping is absolutely useless. I've shipped and had shipped a number of tube amps over the years, and all of them had the tubes inside and none of them have ever had a problem. Not saying you'll never have a problem, but if you can have a problem with the tubes being inside the amp, you can also have a problem with the tubes being shipped separately. That said, I wouldn't worry too much about which tube goes where. As long as you have the proper type of tube for each socket, you should likely be good to go.
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I prefer this method. If they are going to break they are going to break. Proper packaging is the number one defense to prevent damage.
 
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#16
JimmyM said:
Honestly, I think pulling the tubes when shipping is absolutely useless. I've shipped and had shipped a number of tube amps over the years, and all of them had the tubes inside and none of them have ever had a problem. Not saying you'll never have a problem, but if you can have a problem with the tubes being inside the amp, you can also have a problem with the tubes being shipped separately. That said, I wouldn't worry too much about which tube goes where. As long as you have the proper type of tube for each socket, you should likely be good to go.
Click to expand...

I'm not going to say that you're wrong, but this could be kinda like the old "duck and cover" mentality. If you ship with the tubes in, it'll probably still be okay, but might have a slightly higher probability of damage than with tubes out, such that somebody who ships lots of amps might have an incentive. Just like with duck and cover, you're probably still dead or at least injured, but the likelihood of that death/injury is statistically significant in larger numbers.
 
#17
pie_man_25 said:
I'm not going to say that you're wrong, but this could be kinda like the old "duck and cover" mentality. If you ship with the tubes in, it'll probably still be okay, but might have a slightly higher probability of damage than with tubes out, such that somebody who ships lots of amps might have an incentive. Just like with duck and cover, you're probably still dead or at least injured, but the likelihood of that death/injury is statistically significant in larger numbers.
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You guys worry too much :)
 
#19
JimmyM said:
Honestly, I think pulling the tubes when shipping is absolutely useless. I've shipped and had shipped a number of tube amps over the years, and all of them had the tubes inside and none of them have ever had a problem. Not saying you'll never have a problem, but if you can have a problem with the tubes being inside the amp, you can also have a problem with the tubes being shipped separately. That said, I wouldn't worry too much about which tube goes where. As long as you have the proper type of tube for each socket, you should likely be good to go.
Click to expand...

Leaving the tubes socketed can damage the sockets more than the tubes if the shipping is rough. If the pin gaps widen, they cause all sorts of intermittents, and then the socket has to be replaced. :(

I've only seen it happen once with miniature tubes, but I've seen it a number of times on octal tubes, since the tube pins don't bend like the miniature tubes, and they have more mass to swing around. Tube retainers keep the tubes in their sockets, but they won't protect against socket damage.
 
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#20
okcrum said:
Leaving the tubes socketed can damage the sockets more than the tubes if the shipping is rough. If the pin gaps widen, they cause all sorts of intermittents, and then the socket has to be replaced. :(

I've only seen it happen once with miniature tubes, but I've seen it a number of times on octal tubes, since the tube pins don't bend like the miniature tubes, and they have more mass to swing around. Tube retainers keep the tubes in their sockets, but they won't protect against socket damage.
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One of my amps would blow the HV fuse if I played it on top of a speaker. The first time this happened, the amp just made a little zzt sound and the fuse opened up. The second time this happened the tubes arced and produced a bright flash of light, and the sound from the speaker was kind of like a nearby lightning strike. I thought for sure the tubes were shorted.

I pulled the tubes, replaced the fuse, and checked the operating voltages in the amp. Put the tubes back in and they powered up fine. Luckily my hardware store had a tool that looks like a dental pick that allowed me to re-tension the pins in the tube sockets. Now the amp works fine.

I have a fairly large collection of tube amps, and all of the output tube sockets appear to have pins that can be re-tensioned. Probably not good to do this frequently as I would expect the pins to fatigue and break.

Some of the small signal tube sockets do not have room enough to re-tension the pins.
 

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