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Ampeg B18-n PROBLEM!! HELP!!

T

TheDice951

Aug 23, 2013
9
0
#1
hello,
Long story short, I received my Ampeg B18-n s/n 310175 from my grandfather before he died about 10 years ago. I played bass then but had a Hartke pro series 4/10 w/ 500w head so I didnt use it. I am now wanting to use it since I have been reading that it sounds AWESOME. but mine doesn't......

first off, the amp works, all the tubes light up and I can play through it BUT, the amp sounds "Farty" not even halfway turned up? in all honesty, it sounds like crap.... I want to fix this

second, one of the RCA 7027a power tubes started smoking, I pulled it and the amp still worked. I am going to samash tomorrow to get a replacement. the amp sounded crappy before this happened. if any of the other tubes would cause this I would like to see if I can replace that too....

third, I cant seem to find any info on MINE? none of the pics look like mine? the pic is below. the screen was replaced by me when I got it 10 years ago, it was the black mesh. the head even looks different???

I just want this fixed and want to do it myself. please help!!



securedownload_zpseaf41dd7.jpg


<a href="http://s860.photobucket.com/user/zackattk/media/securedownload_zpseaf41dd7.jpg.html" target="_blank"><img src="http://i860.photobucket.com/albums/ab166/zackattk/securedownload_zpseaf41dd7.jpg" border="0" alt=" photo securedownload_zpseaf41dd7.jpg"/></a>
 
#5
The last 3 knobs are for the second channel, if they aren't doing anything your second channel is dead - either components or tubes (second tube should be for channel 2). Or you aren't plugged into the second channel - the first two inputs are for channel 1, the third for channel 2, your picture shows you plugged into channel 1.

With the volume knob at noon you should be in distortion territory on these amps. I'd guess given it's age it needs a cap job and probably some other repair work. I'd bring this to a tech ASAP and not just drop a new tube in there.

Edit - also, the chassis looks either really dirty or really rusty. Transformers look like replacements, as well. Seems it's had some work done over time.
 
#6
its pretty dusty and has been painted so maybe when work was done? I would like ot try and repair myself. I am more than capable, I just need to know what I am doing parts wise.

anyone have a repair manual or anything for one of these? also are there any mods I can do to make it a bit better?
 
#7
the First tube was smoking when I had it plugged in the ch1 port pictured, I removed it and it still played.... I swapped the tubes and the same tube smoked in the other socket. I still could play in ch1 with the tube removed... normal?
 
#8
Amps don't have manuals like say a car. There should be a schematic attached to the amp. If you don't know how to read it then you should not be playing around with the high voltages in the amp chassis. It is a valuable amp restored to full function but much less if modified. BEST mod is to restore it.
 
#9
TheDice951 said:
the First tube was smoking when I had it plugged in the ch1 port pictured, I removed it and it still played.... I swapped the tubes and the same tube smoked in the other socket. I still could play in ch1 with the tube removed... normal?
Click to expand...

Tubes don't "smoke" unless it is just something on the glass. If you saw smoke coming up from under the tube then other components were burning (which a bad tube can cause to happen).

Here is a "manual".Link Removed which may or may not be your exact unit. It is not a '69 Volkswagen Bug or tabletop radio. ;)
 
#10
no schematics on/in the amp. I will have to download or find it online. (yes I can read them and repair electrical. I do it on F-15's everyday...)

it is def the tube smoking, between the plastic and glass.... I swapped the tube to the other socket and it still smoked. there is nothing on the glass. if you need confirmation I can take a video of it....
 
#12
TheDice951 said:
he tube is more than likely shorting something... either way I need a new one o I pick one up... it would be wise to pick up a new "set" instead of one correct?
Click to expand...

A pair would be best and you will have a "spare" that way. Google "Ampeg B18N schematics" you will find a couple different ones.

No do not run that tube again and with only one output tube it is bound to sound pretty bad.
 
#14
This is the schematic you want

Invalid Link Removed

This is the place you'll want to check out when you go to buy parts. You can find some of the same stuff for the same/lower price from other vendors, but Bruce does a nice job of collecting exactly what you need for each type of vintage ampeg.

The tubes in order left to right from the back are the rectifier (5AR4), two power tubes (7027s), PI (7199), channel 2 gain/tone (6SL7), channel 1 gain/tone (6SL7). They should be labeled on the back of the chassis but it may have been removed when it was painted. Like I said earlier, both transformers are replacements, they should be in cans. It's hard to say what other work/mods may have been done.
 

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