Fixing a Bassman 400 210 combo

[nabilhuakbar]

Hey all,

I'm not too familiar with the inner workings of amps and all of that, so I'm wondering if someone smarter than me could help me out. I got a Fender Bassman 400 amp for basically free in a deal with the understanding that something was wrong with it that was probably fixable.

So I plugged it in -- amp turns on, so that's fine. I can run a signal out to a different cab and I get sound, so that's all good. But when I just run the amp by itself, I get no sound at all to the 2x10 speakers built in.

Any ideas of what to check for? I've replaced the fuse and that hasn't made anything work.

After that I need to replace a few pots -- it looks like this amp fell on its face and it's broken off a few knobs and the pot shafts completely and bent up a bunch of others.

 

[DWBass]

Check the speaker connections. A wire or 2 may have come loose.

 

[nabilhuakbar]

Now...here's the kicker. How would I go about doing that?

I can get the amp head out just fine, but the cab looks like it's totally sealed shut. I can't find anywhere to crack it open.

 

[DWBass]

Most likely have to go in from the front. Will need to remove the grill, then remove and inspect each speaker.

 

[BogeyBass]

Remove the grill and speaker.
Be access from the speaker cutout.

Someone might have just blown the factory speakers. Or wiring issue.

I'll assume it has a tweeter. So expect to find a board for the crossover. Most likely board issue. Connections, solder joints, cooked tweeter plug etc etc.

Just a guessing game on the net. Good news is sounds like the amp works. Most likely toasted speakers.

 

[BassmanPaul]

How do the internal speakers connect to the amp? If it's using a 1/4" plug, unplug and put a 9V battery across the tip and sleeve. There should ve a hearty thump from the cabinet.

If not carefully remove each driver and connect the battery across it's terminals Again it should thunk.

 

[nabilhuakbar]

How do the internal speakers connect to the amp? If it's using a 1/4" plug, unplug and put a 9V battery across the tip and sleeve. There should ve a hearty thump from the cabinet.

If not carefully remove each driver and connect the battery across it's terminals Again it should thunk.

This seems pretty easy, I'm gonna give it a shot and report back

 

[BassmanPaul]

Be very very careful unscrewing the drivers. It's so easy for the screwdriver to slip and punch a hole in the cone. That's sure to ruin your day!!

 

[nabilhuakbar]

So I took off the grille and removed one of the speakers -- and it wasn't connected.

After connecting it, I reassembled the speakers and turned 'er on...no dice. No sound.

I wonder if there's an issue with the fuse holder. That's the one thing I can think of that doesn't seem right...it wobbles around a lot (but the connections themselves look okay) and it almost kind of looks like the fuses I have for it are just a tad too short to make contact.

Here's some pics for fun!

The speaker that wasn't connected before. White = + and Black = -, right?

Wiring of Other speaker -- From the thing at the back of the amp to the speaker, and then a line out to the other speaker.

Wiring to the Tweeter

Back of the amp:

Line in looks fine, lines out to the tweeter and speaker seem fine, Fuse wiring also seems fine.

Fuse Holder

End cap with a 2A 250V Fuse in it:

Not sure if there's anything else to look at. I've messed with the Horn Level dial to make sure it wasn't just turned to 0. While messing with the amp and testing out stuff, I DID get a pop out of the speakers when I maxed out the gain. Once. When I'm using the output and wire out to another amp, it works just fine. I see the little clipping light blink when I touch the tip of the jack of the cable that I have plugged in...so the Amp is getting a signal in and it has no problem sending out to something else.

Any other ideas?

 

[gitfiddl]

Hey all,

I'm not too familiar with the inner workings of amps and all of that, so I'm wondering if someone smarter than me could help me out. I got a Fender Bassman 400 amp for basically free in a deal with the understanding that something was wrong with it that was probably fixable.

So I plugged it in -- amp turns on, so that's fine. I can run a signal out to a different cab and I get sound, so that's all good. But when I just run the amp by itself, I get no sound at all to the 2x10 speakers built in.

Any ideas of what to check for? I've replaced the fuse and that hasn't made anything work.

After that I need to replace a few pots -- it looks like this amp fell on its face and it's broken off a few knobs and the pot shafts completely and bent up a bunch of others.

IIRC, the signal from the amp goes to the "tweeter control board" mounted in the center of the back of the cabinet. I believe the crossover is also a part of that assembly. Something may have come unplugged from there, or something may have gone bad. I've got all those parts from a Bassman 250/210 in a box around here somewhere. I know the amplifiers themselves are different, but I'd bet the crossovers/L-pad themselves are the same. If you think that may be your problem , let me know and we can work something out.

 

[nabilhuakbar]

I'm not super knowledgable on these amps but I don't really think it could be anything else. Either the fuse container for the Horn isn't working, or I have the wrong fuse cap in there (but still...I should be getting SOMETHING, you'd think) or maybe something else on that control board is bad. I have no idea how you'd go about isolating that, but I'd be willing to try to work something out as well.

 

[azureblue]

before you go taking stuff out, disconnect the speakers from the amp, and touch a 9V battery to the speaker wires. Not hold it, just touch - the speakers should jump and the tweeter should crackle. If not then disconnect the 10" speakers from the cross over and repeat. From your description, your tweeter control may be going bad. I would try bridging it and see if you get a signal from teh amp. Don't trust a fuse until you have checked it - I had one come loose up in the end cap - it looked good but no. Use your 9V battery and touch both end caps and see if you get a spark - if not - fuse issue.

 

[agedhorse]

The fuse and tweeter level control is for the tweeter only, doesn't explain why there's no sound to the 10" drivers.

Are these drivers wired in series or parallel? If it's series, all it will take is one driver to fail and both won't work.

 

[Razman]

before you go taking stuff out, disconnect the speakers from the amp, and touch a 9V battery to the speaker wires. Not hold it, just touch - the speakers should jump and the tweeter should crackle. If not then disconnect the 10" speakers from the cross over and repeat. From your description, your tweeter control may be going bad. I would try bridging it and see if you get a signal from teh amp. Don't trust a fuse until you have checked it - I had one come loose up in the end cap - it looked good but no. Use your 9V battery and touch both end caps and see if you get a spark - if not - fuse issue.

This is what I do before buying a speaker, I check it with a 9v to see if they all work. Also, get a digital multimeter and check continuity with the speakers. You can also check the individual drivers using the 9v trick to see if individually they work - then move back up to the panel on the back.

BTW I have the exact same combo and IT IS A TOTAL BEAST!! You'll see when you get it working. Tons of low end; too much really, but perfect for some contexts. Really sounds good at home, every bass I have sounds great through it.

Back to troubleshooting - I'd start with each speaker including the HF driver and ensure they are working, then check the continuity of the wiring, etc. back to the plug itself. I recently acquired a Henry the 8x8 and when I tested it, only the top two and bottom two pairs of speakers worked. My hunch was wiring, and sure enough when I pulled out the back panel and peeked inside the wires were off the speaker posts in the middle.

However, when I reached in to reattach them I noticed they were loose - so I went ahead and pulled each driver and checked all of them, wound up replacing one spade connector and 'tightened' up all the rest. Now I play that cab with confidence.

Something else to note - when I got mine, the input jack was sketchy and the output DI didn't work. I had to pull both boards out and re-solder those jacks back to the board as all the joints were cold. When you go to replace the pots I'd inspect any other solder joints and touch them up, if you are skilled at doing so. No micro-soldering on these old things so they are easy to work on. Just don't lose any of the nuts from the front pots - there are a lot of them!

Let me know if I can be of further assistance.

Raz

 

[Downunderwonder]

It ain't the main fuse.

There's a lot of shadowing in the pic that might be shadows or might be smoke.

The soldering on the speaker looks like it was done by a demented chimpanzee.

I am going with someone blew up the stock speakers, put in some replacements, blew those up too and gave up on it.

It's a bit of a leap to there. Investigate whether they are series or parallel hookup so you know if you might only be dealing with one blown before you remove a good one.

It will be easier to get some crimping push on spade connectors for your wires and terminals rather than solder.

 

[nabilhuakbar]

before you go taking stuff out, disconnect the speakers from the amp, and touch a 9V battery to the speaker wires. Not hold it, just touch - the speakers should jump and the tweeter should crackle. If not then disconnect the 10" speakers from the cross over and repeat. From your description, your tweeter control may be going bad. I would try bridging it and see if you get a signal from teh amp. Don't trust a fuse until you have checked it - I had one come loose up in the end cap - it looked good but no. Use your 9V battery and touch both end caps and see if you get a spark - if not - fuse issue.

Yeah it looks like it's wired in series...it goes from the control board to the left driver and then from the left driver to the right driver.

It ain't the main fuse.

There's a lot of shadowing in the pic that might be shadows or might be smoke.

The soldering on the speaker looks like it was done by a demented chimpanzee.

I am going with someone blew up the stock speakers, put in some replacements, blew those up too and gave up on it.

It's a bit of a leap to there. Investigate whether they are series or parallel hookup so you know if you might only be dealing with one blown before you remove a good one.

It will be easier to get some crimping push on spade connectors for your wires and terminals rather than solder.

Yeah that's not shadows from the pic...so you're saying that's scorching?

The wires are all using spade connectors already, nothing appears to be soldered internally. I dunno if that's supposed to be stock or not, this amp is coming up on 20 years almost and it's definitely been abused a bit. It's fallen over on it's front at least once and I'm gonna need to replace 6 or 7 of the pots to get them fully functional again.

Honestly I may just end up getting a separate cab and running the amp to that.

 

[JeezyMcNuggles]

So I took off the grille and removed one of the speakers -- and it wasn't connected.

After connecting it, I reassembled the speakers and turned 'er on...no dice. No sound.

I wonder if there's an issue with the fuse holder. That's the one thing I can think of that doesn't seem right...it wobbles around a lot (but the connections themselves look okay) and it almost kind of looks like the fuses I have for it are just a tad too short to make contact.

Here's some pics for fun!

View attachment 3950041

The speaker that wasn't connected before. White = + and Black = -, right?

Wiring of Other speaker -- From the thing at the back of the amp to the speaker, and then a line out to the other speaker.

View attachment 3950044

Wiring to the Tweeter

View attachment 3950045


Back of the amp:

View attachment 3950046

Line in looks fine, lines out to the tweeter and speaker seem fine, Fuse wiring also seems fine.

Fuse Holder
View attachment 3950047

End cap with a 2A 250V Fuse in it:

View attachment 3950048

Not sure if there's anything else to look at. I've messed with the Horn Level dial to make sure it wasn't just turned to 0. While messing with the amp and testing out stuff, I DID get a pop out of the speakers when I maxed out the gain. Once. When I'm using the output and wire out to another amp, it works just fine. I see the little clipping light blink when I touch the tip of the jack of the cable that I have plugged in...so the Amp is getting a signal in and it has no problem sending out to something else.

Any other ideas?

I had a problem with an old 15 combo where I wasn't getting sound out of the speaker. I did the same thing, pull it out and reconnect it. Everything seemed fine, but no sound. But, the amp worked fine besides that. Running out of the pre out, I had sound. Same with the headphone out. Never figured it out, and threw it away. Hope you don't have to do that.

 

[JeezyMcNuggles]

The clip is supposed to be on the peg (attached to it), not under it.

is this the only one like this? Or...

Cause the positive on the tweeter is hanging off the post. That's a bad connection. If the other speakers look the same, pull them off,, squeeze the clips together, lightly, and try to get better connections.

 

[Razman]

Yeah it looks like it's wired in series...it goes from the control board to the left driver and then from the left driver to the right driver.



Yeah that's not shadows from the pic...so you're saying that's scorching?

The wires are all using spade connectors already, nothing appears to be soldered internally. I dunno if that's supposed to be stock or not, this amp is coming up on 20 years almost and it's definitely been abused a bit. It's fallen over on it's front at least once and I'm gonna need to replace 6 or 7 of the pots to get them fully functional again.

Honestly I may just end up getting a separate cab and running the amp to that.

When all is said and done if you wind up disliking it that much feel free to use my FedEx account number to have it removed from your residence and re-homed.

 

[nabilhuakbar]

I had a problem with an old 15 combo where I wasn't getting sound out of the speaker. I did the same thing, pull it out and reconnect it. Everything seemed fine, but no sound. But, the amp worked fine besides that. Running out of the pre out, I had sound. Same with the headphone out. Never figured it out, and threw it away. Hope you don't have to do that.

If I can't get the speakers running I can still at least use this amp and run it out to a different cab. I got it for basically free so if I have to drop a few hundo on a 4x10, oh NOOOOO now I have an amp and cab setup that's functional but a little cumbersome.

The clip is supposed to be on the peg (attached to it), not under it.View attachment 3950316 is this the only one like this? Or...

Cause the positive on the tweeter is hanging off the post. That's a bad connection. If the other speakers look the same, pull them off,, squeeze the clips together, lightly, and try to get better connections.

Fantastic catch, I'll pull the other driver out tomorrow and check it as well. If one of them is hooked up wrong, chances are pretty good that another wire clip somewhere in there is jacked up as well