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Are my old 66 Jensen Gold Labels shot?
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Brian



Joined: 22 Aug 2006
Posts: 1361
Location: Southern California

PostPosted: Mon May 05, 2008 2:23 pm    Post subject: Are my old 66 Jensen Gold Labels shot? Reply with quote

I had my 66 Vibrolux Reverb out for a gig this weekend and it worked OK ...but I started noticing the residual distortion especially noticeable at low volume. I went through the gig but noticed that the amp seemed underpowered and was breaking up and farting out...almost like an old tweed deluxe. I got it home and checked all the tubes and they seem OK. It already has had a cap job so that can't be the issue....

I took the Jensen Gold Labels C10NS speakers out and inspected them...there was a ton of old dust which I carefully removed. I saw no tears in the cones although they look real old and dry and somewhat dirty... I put it back together and made sure the bolts were all snug...Plugged it back in and its still there....maybe not quite as bad at low voume but when you push it you can hear it farting out on the bass notes. This amp never used to this... Any ideas??
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Dogbear



Joined: 23 Jun 2007
Posts: 275
Location: Florida

PostPosted: Mon May 05, 2008 7:08 pm    Post subject: Reply with quote

Brian, my first step would be to isolate the problem. Hook the amp to another set of speakers, if it continues to exhibit the problem, then it's the amp. If not, it's most likely one or more of the speakers. I had a Peavey cabinet with Black Widows in it that did the same thing. One of the Black Widow's was partially blown and had to be re-coned. Sometimes the damage is inside the coil where you can't see it. Pushing the speaker cone in and out should be smooth and not have any "scratchy" feel what so ever.
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Brian



Joined: 22 Aug 2006
Posts: 1361
Location: Southern California

PostPosted: Mon May 05, 2008 8:55 pm    Post subject: Reply with quote

thanks Mike. Last nite I did hook up another 2x10 cabinet to it but it was back to back...The sound out of the other cabinet did sound better but also some of the sound coming out of it's back made the VR's cabinet speakers vibrate sympathetically. I need to try and physically seprate them more. I think you are correct that the voice coils may be tired or blown. Does that usually mean a complete speaker overhaul? recone etc
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Dogbear



Joined: 23 Jun 2007
Posts: 275
Location: Florida

PostPosted: Mon May 05, 2008 9:37 pm    Post subject: Reply with quote

If the speaker is partially blown, the only thing you can do is have it professionally repaired or re-coned. The most common types of non visual damage are fatigue or burnt voice-coils/rubbing. Depending on the speaker type, most companies have drop in voice coils and baskets made for all name brand high end speakers. Since the cost is anywhere from $75 to $100 a speaker, nobody repairs cheap speakers. My Black Widow was $80. Here is a link that discusses the topic fairly well.

BTW, re-coning can dramatically change the sound of an older speaker. Sort of like retopping a guitar. Takes time to break in.

Hope it turns out to be something more simple.

http://www.colomar.com/Shavano/recone.html
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Silverface



Joined: 23 Aug 2006
Posts: 324
Location: Hermosa Beach CA

PostPosted: Wed May 07, 2008 4:52 am    Post subject: Reply with quote

Quote:
Since the cost is anywhere from $75 to $100 a speaker


Man, are you shopping at the wrong place for reconing services.

Weber (www.tedweber.com) - who not only recones but properly remags the speakers - charges $55.00 for 10" speaker. I have had several recones from them and several from Orange County Speaker, and IMO there's no comparison - Ted Weber *understands* guitar speakers and does them right.

Brian, one thing I learned from Ted is that otherwise perfectly good 40-50 year old speakers will have lost AT LEAST 50% of their power handling even if nothing is otherwise wrong with them. These are DUE for a recone - your voice coils are likely fine (farting out is not a "blown speaker" problem) but the cones have no strength left in them - the binder that holds the paper together dries over decades and becomes very weak...hence the low-note fart-fest. Oddly, while you don't want a lot of humidity around metal amp parts or circuit boards, humidity is GOOD for speakers and helps their longevity.


I have an original pair of P10Q's that we estimate can handle about 10-12 watts each at this point. I'll have to have them reconed before using them.

But $75-100 for a 10" recone is ridiculous! Black widows are expensive to recone because it's not a stock "recone" - there's a whole basket kit that's replaced. It's a diferent operation - and still does nothing to re-power the magnet.
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Brian



Joined: 22 Aug 2006
Posts: 1361
Location: Southern California

PostPosted: Wed May 07, 2008 5:21 am    Post subject: Reply with quote

I temporarily took out the Jensens and installed a Weber Califiornia 10 and Eminence Copperhead. I think they sound stronger and better but not 100% sure...since when I hit a low not now I hear a buzzzzzz . I have no idea what that is or if it was what I was hearing before. It might be more than one thing. I am not certain there's is nothing else wrong tube wise either...kind of tough to know without new tubes to try or a tube tester.
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Dogbear



Joined: 23 Jun 2007
Posts: 275
Location: Florida

PostPosted: Wed May 07, 2008 3:47 pm    Post subject: Reply with quote

Silverface, those prices are close to what a major rebuilder is getting in Tampa for rebuilding quality speakers. I'm sure there are better and cheaper places. I totally agree on old magnets. Black Widows were a bad example, however; the informational link I posted did identify that they were different. As I stated, the most common problems are fatigue (old age/dry rot, etc.) or burnt voice-coils/rubbing. The fix is basically the same for all of them. Voice coils may or may not need to be replaced depending on condition, but; why replace only part of an old speaker? In any case, the rebuilder will tell you what is needed. As I get older, I try not to burn up as many as I use too.
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Doc62049
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PostPosted: Thu May 08, 2008 3:22 am    Post subject: Reply with quote

Could be many different things. I recently had a problem on my twin reverb farting out on low notes. Tubes tested good, bias was set correctly, filter caps good, new speakers. Turns out it was a JJ 6L6 tube that apparently is "weak" or otherwise somehow not handling the power well. Replaced that one tube with a NOS GE and the problem disappeared.
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Raybob



Joined: 26 Aug 2008
Posts: 98
Location: Kyburz, CA

PostPosted: Thu Sep 04, 2008 1:32 am    Post subject: Reply with quote

Brian,
I was curious if you ever figured out the problem with your amp. I have a 68 Deluxe Reverb I restored from guts left in a basement in SF. It was a mess. Someone rewired the reverb circuit to make a distortion or something but the reverb tranny and or the caps leaked all over the chassis. I had to replace three tube sockets from corrosion and thought I had gone over everything. I've been using it a few weeks now but last night, it was loosing power big time. I reached behind the amp between songs and felt one power tube wasn't near as hot as the other. I've done this before, cleaned the socket and tightened the pin holders but the problem came back. I'm sure now I need to replace that socket but hey, it's 40 years old! I'm thinking I have the same problem with my 64 Bassman the last time I used it too. Sad

When you have the problem, try feeling the heat from the power tubes and see if one is not getting as hot.
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Brian



Joined: 22 Aug 2006
Posts: 1361
Location: Southern California

PostPosted: Thu Sep 04, 2008 3:27 am    Post subject: Reply with quote

Thanks Raybob...I went through the amp but couldn't find anything obvious. I haven't had it out to gig lately so I don't know if would happen again. I do have a new set of power tubes handy in case it happens again.
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Silverface



Joined: 23 Aug 2006
Posts: 324
Location: Hermosa Beach CA

PostPosted: Sat Oct 11, 2008 7:24 pm    Post subject: Reply with quote

Quote:
I reached behind the amp between songs and felt one power tube wasn't near as hot as the other. I've done this before, cleaned the socket and tightened the pin holders but the problem came back.


If it came back I'd take a look at the phase inverter circuit (and tube) before messing with the output tube socket again - it would be odd for a tube socket to go repeatedly bad - usually one retensioning every 20 years or so is enough! Check the plate voltage to the output tubes: a bad half of a phase inverter can throw it out of whack; even worse, you could very well have lost your output transformer if those voltages are not pretty close. If something leaked all over the chassis they may have lost filter cap - that can take out the OT partially, where you get intermittent voltage drops or it drops when it heats up.
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Raybob



Joined: 26 Aug 2008
Posts: 98
Location: Kyburz, CA

PostPosted: Sun Oct 12, 2008 5:57 am    Post subject: Reply with quote

Silverface wrote:

If it came back I'd take a look at the phase inverter circuit (and tube) before messing with the output tube socket again - it would be odd for a tube socket to go repeatedly bad - usually one retensioning every 20 years or so is enough! Check the plate voltage to the output tubes: a bad half of a phase inverter can throw it out of whack; even worse, you could very well have lost your output transformer if those voltages are not pretty close. If something leaked all over the chassis they may have lost filter cap - that can take out the OT partially, where you get intermittent voltage drops or it drops when it heats up.


Thanks Jim. The inverter circuit has a new SST in place of the tube and the diode and cap are almost new also. The OT makes sense. When I got the amp, I replaced all caps, all out of tol. resistors and 3 tube sockets from filter cap leakage. I recall cleaning crud from the outside of all trannys except power. I've just changed the 6V6 socket in question and put in all new tubes. Seems to work fine but a gig will tell. Guess if I crank it up at home and jam for an hour or so, that should be enough to see if it's fixed. If not, OT will be changed.
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Raybob



Joined: 26 Aug 2008
Posts: 98
Location: Kyburz, CA

PostPosted: Tue Oct 28, 2008 2:14 am    Post subject: Reply with quote

Jim,
I guess I didn't know what you meant by "inverter" circuit. I assumed you meant at the GZ34 where ac is converted to dc. I was thinking of AC inverters Embarassed . You meant the 12AT7 that feeds the 6V6s. duh. I can and will check that. I recently put all new tubes (after the new 6V6 socket change) and finally got to play the amp yesterday at a birthday party. It worked great until the last two songs, when I heard it completely cut out, then a loud note brought it back. Happened a few times. I'll check the resistors and such in the inverter circuit and look ALL OVER for an intermittent solder connection or bad ground.

Raybob
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Brian



Joined: 22 Aug 2006
Posts: 1361
Location: Southern California

PostPosted: Mon May 04, 2009 3:37 am    Post subject: Reply with quote

I'm reviving this thread exactly 1 year later...

Yesterday I played the same gig as last when I reported problems with my Vibrolux Reverb. Since that time I replaced the all the tubes, re-tensioned and cleaned the sockets, replaced the screen grid resistors...The amp had previously had all it's electrolytic caps replaced. I hadn't noticed any problems any more, but I hadn't gigged it hard either since then. Nevertheless I took the amp out and brought a Tweed Deluxe as a backup...

Last year when I played this same gig, it was having problems...it started to make crackling/sizzling noises and losing power. I made it through the gig but it was really limping along.

At the gig last nite it started doing the same thing....darn! But I brought the Tweed Deluxe clone as a backup. So what I did was un-hook the 2x10 speakers from the Vibrolux Reverb output, and ran another speaker cable over to the Tweed Deluxe cabinet (un-hooked the Tweed Deluxe head) and ran the 1x12 cab with the Vibrolux Reverb head and it sounded great! The 1x12 is an Eminence Cannabis Rex and sounds fantastic! No sign of any more amp problems whatsoever.

The bad news is that it really seems that those old Jensens in the Vibrolux have had it. Does it make sense that this would only show up after the speakers are working hard? Maybe they get hot and it only shows up then?

On one had it does point to the speakers being the culprit...but then there is another factor that would be easy to overlook. When I ran the 1x12 cabinet with the Vibrolux Reverb...is was driving an 8 ohm speaker and not the normal 4 Ohm 2x10 load. Could this difference actually mask an issue with the output transformer? (and maybe not the speakers?)
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Bob Warford



Joined: 24 Aug 2006
Posts: 97

PostPosted: Mon May 04, 2009 5:14 am    Post subject: Reply with quote

This is not exactly your situation, but I recently had major problems with a very high-end set of speakers for my home sound system - old AR speakers that had developed major distortion problems.

I found a place called Orange County Speaker Repair, whose website is http://www.speakerrepair.com/, and took the speakers to them - for about $150, they refurbished both speakers, each with a 12" woofer, 6" (or so) midrange, and a much smaller tweeter (don't remember it's precise size), tested them, etc., and all was done in about 2 weeks.

I'd check with them about your speakers - I was really impressed with their knowledge of speaker construction and dynamics, and their workmanship.

Let me know if you have a good or bad experience with them - so far, mine has been extremely good....

Bob
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