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Post subject: Pro Jr and Hot Rod amps...question about component longevity
Posted: Tue Jul 27, 2010 9:48 am
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i dont know if its me or my ears going numb after a few hours, or what. but i get the feeling that after ive had the pro jr going for a few hours at a gig or rehearsal, it seems like by the end of the night it sounds a bit more hairy. anyone else feel that way? like it sounds like it is getting "tired" and doesnt tolerate being pushed as much as it did when you started that night, if that makes sense. just sounds a bit harsher.

sometimes i assume it might be too much highs in the mix, and sometimes i am right, but other times i dont think its the case.

i dont think its the tubes because i usually glance at them real quick before i shut down to check for redplate. havent had that issue. and then, the next time i use the amp, it sounds great, but push it a few hours and its back to this issue.

i typically run the amp with volume and tone both in the ballpark of 7-9. i rarely dime it (or '12' it). guitar (strat almost always) volume is usually at 7-ish max for typical bar band driven tones, then i up the knob for leads.

i was wondering if this was a heat issue. maybe the heat is rising up and screwing with the components because its trapped in that hotbox of a chassis, with no ventilation. i always have the amp in a wide open area, never backed up against a wall or anything, so thats not the problem.

i'm considering trying having the amp mounted upside down next time i play a prolonged period. i'll have to tilt it for the cable to have room. mounted sideways would be bad i assume, because the tubes will be cooking each other. might there be any consequences to sitting the amp upside down? i heard some amps should not be placed this way because the potting on the transformers can spill out. i wasnt sure if the pro jr had the same issue.

some of you have had PJs and BJs for a long time. have you ever had to replace caps or anything during the duration? can you attest to any of the above? how well can the components used in Hot Rod series withstand the excessive heat?

i try to just play the thing and not worry about it, but i cant help but to think about weird stuiff like that.

thanks


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Post subject: Re: Pro Jr and Hot Rod amps...question about component longe
Posted: Tue Jul 27, 2010 10:58 am
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msvolpe wrote:
.. but i get the feeling that after i've had the pro jr going for a few hours at a gig or rehearsal, it seems like by the end of the night it sounds a bit more hairy.....it sounds like it is getting "tired" and doesn't tolerate being pushed as much as it did when you started that night, if that makes sense. just sounds a bit harsher.

i was wondering if this was a heat issue. maybe the heat is rising up and screwing with the components because its trapped in that hotbox of a chassis, with no ventilation.

i'm considering trying having the amp mounted upside down next time i play a prolonged period. might there be any consequences to sitting the amp upside down? how well can the components used in Hot Rod series withstand the excessive heat?thanks


If the ProJr is like the BJr and HRDlx and HRDvl, the capacitors aren't exactly the best quality. I don't have the ProJr, but I have the other three. I have some caps ordered for the BJr, and a trim pot to set the bias properly as they are biased to hot from the factory. I have already gone through the caps on the HRDlx and checked them. Haven't done much to the HRDvl. The tubes in the BJR are JJ's with a Fender label, so I would think that they are good quality. Not sure about the ProJr tubes.

I would definitely check the caps, and check the bias for the output tubes, to see if they are running hot (I suspect they are running hot). There are various kits available on the internet for upgrading the caps for more reliability and more stable tone. Google "Pro Jr mods". If the tubes are biased to high that can cause premature failure of the tubes and even other components.

It sure sounds like a heat related problem that I would definitely check into before just changing the tubes. It makes me cringe to say this, but I have heard of people putting a fan blowing into the back of the amp to keep it cool, but heat is a symptom, and the fan would be a band-aid. That might get you by for awhile, but isn't a solution to the problem.

As far as turning the amp upside down, the tubes would still be vertical so I would think that it would be ok. Most new tubes that you buy will indicate whether or not the mounting position matters, vertical, horizontal or doesn't matter. :)
.


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Posted: Tue Jul 27, 2010 11:01 am
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Without knowing more by way of personal hands-on experience with your particular amp I can only say that it certainly SOUNDS like it must be a heat related issue from your description. Being somewhat biased against the HotRod series of amps myself my mind tends to lean towards the lesser quality components used in the HotRods as a probable cause for your issues. Some may object to my reference to lesser quality parts but if they think about it there must be a reason the HotRods are so affordable in comparison to the better amps Fender makes.

As for running your amp upside down I have no factual comment(s) as the thought of doing so has never occurred to me nor have I ever seen it done before so I have absolutely no experience in that regard. My initial gut feeling is that it very well may work to reduce heating since the tubes hang from the chassis and the heat would naturally radiate up to the PCB section while positioned normally but your controls will be unaccessable if you turn the amp over. Somehow I don't think this is advisable. I would suggest turning the amp off between sets and placing a small fan behind the amp blowing inside to help keep it cooler.

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Posted: Tue Jul 27, 2010 1:48 pm
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yea, i guess i'll try messin around with a small fan. it just seemed like i'd be getting too involved/obsessive going that route, so i hesitated to even bother. but i suppose the amount of time i spend thinking about this stuff contradicts that school of thought. so maybe i'll try it.

at that rate however, i'd probably position the fan so that it blows air OUT of the amp. like maybe set it inside the cabinet and blow air out the back. or i could try setting it right against the back, oriented so that it blows away from the amp, thereby sucking the hot air out. i hear blowing air around inside the amp can be bad. dust can find its way inside the chassis.

oh and i am using JJ tubes, just to address a previous post. i forgot that info.

upside-down amp does seem to raise a red flag, i agree. and its not ideal to do, however i figured id apply some simple physics and ponder that notion. heat rises, so let it rise away from the chassis, right? but true, that idea has its downsides.

i have to wonder why these manufacturers dont just put the chassis on the floor of the amp, and the tubes on top of it. you'd have to be sure to protect the inside from dirt, and you'd have to come up with a practical way to mount the pots, but otherwise, i see no reason not to do it.
eh, maybe it ain't necessary.
but if anyone building an amp uses that idea, i demand a royalty :roll:


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Posted: Tue Jul 27, 2010 3:15 pm
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msvolpe wrote:
.... i hear blowing air around inside the amp can be bad. dust can find its way inside the chassis.

i have to wonder why these manufacturers don't just....


Great point! Dust, [s]beer[/s], err, I mean milk, soda and other liquids and all sorts of nasty things can be blown into the amp.

Maybe the manufacturers want to sell replacement parts.....? :lol:


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Posted: Tue Jul 27, 2010 3:40 pm
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I had blown power supply caps in my HRDlx in just a few months as well as a myriad of other components. Most of the components as well as the boards in these leave a lot to be desired in these amps. I took advantage of a trade in trade up deal after I sold it privately. That was the only way I could fix it for good. :wink: The trannies are decent enough though.

This is the only way to fix a HRD series amp and keep it at the same time.

http://www.tjadamowicz.com/amps/process.html

TJ is a master of his craft. :D

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Posted: Tue Jul 27, 2010 3:40 pm
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BMW-KTM wrote:
my mind tends to lean towards the lesser quality components used in the HotRods as a probable cause for your issues. Some may object to my reference to lesser quality parts but if they think about it there must be a reason the HotRods are so affordable in comparison to the better amps Fender makes.


There was a period within my lifetime when virtually every part used in every Fender amp was MIL-SPEC GRADE -- from the Vibrochamp to the Dual Showman.

And most of those amps will still be "amping" well after I've been committed to a dirt nap.

I'll consider it an epiphany if that philosophy once again prevails over today's amp designers.

Arjay

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Posted: Tue Jul 27, 2010 4:08 pm
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msvolpe wrote:
... i have to wonder why these manufacturers dont just put the chassis on the floor of the amp, and the tubes on top of it. you'd have to be sure to protect the inside from dirt, and you'd have to come up with a practical way to mount the pots, but otherwise, i see no reason not to do it.
eh, maybe it ain't necessary.
but if anyone building an amp uses that idea, i demand a royalty :roll:


Many amps are already built this way with the tubes pointing up and away from the main chassis. Sorry, you'll have to find another way of getting royalty cheques.

:wink:

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Posted: Tue Jul 27, 2010 7:19 pm
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i'm currently exploring the idea of getting a small pc fan. but now i might be confusing myself.

my question right now is...what components in the amp are heat sensitive, and thereby will affect the tone as i described when overheated?
i alluded to it, but not based on personal knowledge, so i need to verify the facts. my assumption is caps and trannies

well anyway, i was wondering just how effective is it really to have a fan blowing the air within the cabinet, when meanwhile, the caps upstairs locked up in that chassis without ventiliation are probably stilll baking? im not so sure that blowing hot air off the tubes will have direct impact on the chassis interior. right?

however, if the trannies are a problem area, then yes, fan blowing heat out of cabinet should help. but i need an answer to the above question. until then, i dont really know what the fix is.

i was trying to find out where the fan is mounted on the peavey C50 as an example, but i had troiuble finding that info. anyone know?

thanks


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Posted: Tue Jul 27, 2010 7:39 pm
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msvolpe wrote:
i'm currently exploring the idea of getting a small pc fan. but now i might be confusing myself.

my question right now is...what components in the amp are heat sensitive, and thereby will affect the tone as i described when overheated?
i alluded to it, but not based on personal knowledge, so i need to verify the facts. my assumption is caps and trannies

well anyway, i was wondering just how effective is it really to have a fan blowing the air within the cabinet, when meanwhile, the caps upstairs locked up in that chassis without ventiliation are probably stilll baking? im not so sure that blowing hot air off the tubes will have direct impact on the chassis interior. right?

however, if the trannies are a problem area, then yes, fan blowing heat out of cabinet should help. but i need an answer to the above question. until then, i dont really know what the fix is.

i was trying to find out where the fan is mounted on the peavey C50 as an example, but i had troiuble finding that info. anyone know?

thanks


The problem is cheap boards and tubes improperly mounted to them. Lots of manufacturers mount tube sockets to PCB's with no problems at all. The boards should be thick, double sided boards with plated through holes. The HRD series PCB's are thin, single sided boards. The board flexes too easily too. Components that generate heat should have heat sinks. My Egnater has them on critical components. My HRDlx didn't.

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Post subject: Compnents
Posted: Tue Jul 27, 2010 11:47 pm
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msvolpe wrote:
my question right now is...what components in the amp are heat sensitive, and thereby will affect the tone as i described when overheated?

i'm not so sure that blowing hot air off the tubes will have direct impact on the chassis interior. right?

thanks


63supro is right, the thin circuit boards used in the Hot Rods are a weak area in the amp. The solder joints tend to crack and cause problems, examine them closely. Almost all of the heat in the amp is from the transformers and tubes. That heat is what "cooks" the circuit boards, and causes cracked solder joints to get worse and accelerates the deterioration of caps inside the chassis. The heating and cooling cycles from normal use causes any problems to get worse over time.

You don't really need air movement inside the chassis where the components are, you just need to reduce the amount of heat that radiates from the tubes and transformers up to the bottom of the chassis. So, I would say there are three areas of concern. 1) Bias tubes properly, this will reduce heat. 2) Check for cracked solder joints and for heat damage to circuit boards (brown spots of discoloration) 3) Check the capacitors, both value and for leakage. The capacitors are just about as easy to change to better quality caps, as it would be to unsolder one side of them so they can be checked. You might need a good tech if you are uncomfortable inside an amp, or don't have the equipment.

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Posted: Wed Jul 28, 2010 5:29 am
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Some of the components get pretty hot too. The 5 watt power resistors actually can scorch the board and lift the traces over time. Fender should have either used heat sinks or raised the resistors off the board to allow air flow. Fenders been hanging the chassis upside down for decades with no real heat issues until they started building tube amps to lower price points for higher profits. The HRD series is a decent idea that just lacks in execution.

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Posted: Thu Jul 29, 2010 5:53 am
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Retroverbial wrote:
BMW-KTM wrote:
my mind tends to lean towards the lesser quality components used in the HotRods as a probable cause for your issues. Some may object to my reference to lesser quality parts but if they think about it there must be a reason the HotRods are so affordable in comparison to the better amps Fender makes.


There was a period within my lifetime when virtually every part used in every Fender amp was MIL-SPEC GRADE -- from the Vibrochamp to the Dual Showman.

And most of those amps will still be "amping" well after I've been committed to a dirt nap.

I'll consider it an epiphany if that philosophy once again prevails over today's amp designers.

Arjay
I agree,but with tubes I guess we're s.o.l. when it comes to Mil-spec nowadays,unless it's another country's mil-spec.
I think I've read that other militaries still use tubes in Europe or wherever,and that's why they're still made...is that the case?


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Posted: Thu Jul 29, 2010 8:58 am
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Most of the countries using Soviet/ComBloc military gear have finally made the leap into the 21st century and are buying solid-state equipment. I think the chicom and Eastern European vacuum tube manufacturers are now catering to us amp junkies and hi-fi addicts to near-exclusivity.

Arjay

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Posted: Thu Jul 29, 2010 9:32 am
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I sometimes wonder if the solid-state technology is really a leap forward in some cases. I'd bet that a strong enough EMP would take out the SS circuitry while the "old" tubes would just keep chugging away. :?: Static seems to mess with SS equipment. I've had a few SS home stereo's that would lock up just because I walked across a carpeted floor to turn them up. The only ill effect from static on my tube amp when I touch it, is a slight tick of sound from the speaker. But, SS is more efficient, and is cheaper.....isn't it always about the money? :wink:

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