6BQ5 REPLACEMENT

Noticing my audio (pep) on my Sonar dropping after about ten minutes of use. Would this suggest a
soft drive (12at7) or one of the two push pull 6bq5's? If 6bq5 Is it wise to replace a 6bq5 with the likes of a el84 or 6014 (advertised as a true 6bq5 replacement (Chinese) when it's going to be used for transmitter audio purposes?
Or should I purchase a straight up 6bq5. Damn 6bq5's have gotten expensive! I've a few parts rigs, but hate to pull tubes I can't test only to find out the ones I pull are worse off then the one I might have to replace. Its not that easy for me. Purchhesing a tested or new replacement is much easier.

ExitThirteen said:

It is possible that the 12AT7 could be soft, but I'd more likely suspect the 6BQ5's. You can replace those with EL84's, as it is the same tube. Most music stores carry EL84's and can be sold as matched sets, which would be ideal for your Sonar. If you replace just one tube, replace it with a 6BQ5. If you do decide to replace both 6BQ5's, then you can go for the EL84's. Not recommended to replace just 1 tube.

~Cheers~

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I like my can't wait a minute for anything purchesed a 12at7. It was tested on a Hickock, and described by the tube seller as nos. $5 free shipping. I figured what the hell. Maybe I'll purchase two 6bq5's from the seller link you dhares, and replace all three. Two 6bq5's and the 12at7. I thought it might've been either the 12au6 or 12aq5 in the Demco (modulator.) But with the Demco in the out position the sonar is still dropping from 17 watts pep to 10. I will change out the 12at7 and both 6bq6's in a single sessiont. I know this might sound unnecessary to most but you have to understand my disability makes it impossable to do myself. Having the yl doing the change all at once makes it easier on me as I don't like having to ask although my xyl would change out every tube in the rig one at a time over whatever time period it would take. It's something most are able to do, and might not understand until (good forbid) they one day would have to ask another to do it for them. I just don't want anyone to think i might be changing out good tubes without reason. I'll use that link shortks. And most likely will be buying two 6bq5's. Thanks my friend. 73's

Onelasttime said:

Find someone with a tube tester in your area and test your tubes before you start blowing money left and right tossing parts at it.

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There's no one I know with a tester. I've a few parts FS 23's. But having to trubble the xyl to dig them out of the closet then have to take the chance that they're tubes are any good isn't worth it to me. I'd rather purchese two new or nos one's. Problem I'm finding is so many different brands. Even on the links shared all write-ups are for (guitar) musical instruments amps. I'm not sure if there's a particular brand that will keep this rig sounding loud yet offier that war soft sound like the ones that are currently in there. If anyone can suggest a company brand I'd appreciate it. These parts rigs are burried and to my memory do have two 6bq5's. Only one is a final and the other a modulator. So I'll assume they're not mathed. I'm not rushing it because even though I reported the pep to be 17 (and have been for some time) it's actually 12 but within 15 minutes of use drops down to 7 watts pep. I don't think the lost 4 watts is making any difference. It sertainly isn't as far sa driving the amp. I just feel it and any equipment I own should be working to it's optimal potential. Any advice is appreciated. PS. I already purchased the 12at7. Nos $5 shipped 60 day guarantee. Money back no questions asked.

Are el84/6bq5's exactly the same as a straight up labled 6bq5? This is important to me. If there's the slightest differeance I will go with a matched pair of 6bq5's as opposed to el84/6bq5's. Unless someone who knows for sure there is absolutely no difference says so. Exitthirteen are you 100% positive there's no difference? Thanks.

BJ radionut said:

https://www.tubesandmore.com/products/el84-tube-amp-doctor

https://www.tubesandmore.com/products/el846bq5-tung-sol

These should fit the bill...unless your really serious about OEM, which was most likely RCA or Sylvania made...but your reaching a price break here that is over the top nowadays. The Russian equivalent I have used...work well MHO...
The Tube Dr. brand have good reputation for H/D...though you "MAY" loose a few watts from the PEP top end...(not a big deal) seems you gain in long service usage.
Ultimately your choice, but I like these choices.
All the Best
Gary

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Thanks Gary. Exitthirteen says el84 also. The TAD @ about $20 with shipping# sunds like a good choice for a replacement. I had no intention of using the station last night but did so intentionally in order to see if any locals noticed the difference between the 12 watts pep and the difference after about 10 minutes of use when the audio drops to around 7(pep,) Not one of three stations noticed any difference when asked. I'm going to install the 12at7 when I recive it (on Monday.)
If it's not the driver I'm going to purchase a matched set of the TAD 6bq5's. If is indeed the driver they'll be no need to replace the 6bq5's. Thanks for sharing the link. I've saved the three different sellers shared by you and exitthirthteen.73's

Okay. I want to thank all who replied. My pep has now dropped to about 4 watts pep. Wheather it's the 12at7 drive or one of the push pull 6bq5 modulators I don't kmow but it's going bye bye rapidly. Theses are the matched 6bq5's I've decided to purchase. The 12at7 and matched set of 6bq5's will be here on Monday. I hope I made a good choice. I think so (hope so.)

Rick330man said:

Those RCA 6BQ5/EL84s were top notch. That tube's big brother, the 7189 will take around 400 volts on the plates as opposed to around the 300 to 315 spec on the 6BQ5/EL84. In the case of RCAs, there was a period where they made them all to the more rugged 7189 specs and just sold them as either the 7189 or the 6BQ5. And they are great tubes. I've got an RCA 6BQ5/EL84 pair made in 1960 that still sound amazing.

As for the 12AT7, I am still not convinced the new production ones are as good as those from the golden age of tubes. I bought a box of like 100 1980's production JAN Philips 12AT7s about 15 years ago. When I test them on a Hickock, their numbers are almost always far stronger than any output or transconductance values I get on new production tubes. The JAN Philips 12AT7s are still cheap, so I'd shell out a few extra bucks for these over a JJ, Shuguang or something else currently made.

Good luck.

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I purchased, and already received both the 2 nos RCA 6bq5's and the singal b&k nos 12at7.
I know for sure the RCAcs are vintage 1960's era tubes. I'm not exactly sure when or if b&k stopped producing tubes but if I'd have to guess I'd say it too is vintage. I'm hoping to get a chance to install them today. I will install the 12at7 driver first and test to see if the Modulation will cease to drop from it 12 watts (pep) to what was 4 watts when I last used the transciver.
If the 12at7 doesn't correct the issue I will then replace both 6bq5's with the matched set I bought. I'm hoping these replacements rectify the situation.
If not I can only assume the modulation Transformer might be no good. But my lack of knowledge doesn't allow me to know if this would cause a modulation drop after about 10 minutes of use or the Transformer if bad would not allow any audio at all to get past the audio amplification stage. If it's anything else besides the tubes I will unfortunately have to send it out.
I do have several rarts FS 3023's an 23's. If my memory serves me right the Modulation Transformers in either of those rigs are an exact match for the one In the fs2340.
I've had not a single issue with the 2340 since it was fully restored abuot 3 years ago. Of course this issue occurred 2 weeks after selling my backup 2340. Thats the luck I've got. I think the rig maybe angry at me for selling it's brother (lol.) Thanks for the tube information. PS. I'm going to install the driver (12at7) first on the advice of another member who also replied to this post. He was of the opinion that if it was a tube it would most likely be the driver causing the Modulation to drop down after about 10 minutes of modulating.

Shadetree Mechanic said:

Bump. The peak power on my 2340 is down to about 8 and it used to be 12. I am thinking about replacing the 6BQ5 final tube. Sonar, what did you do to fix your problem?

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Chris. The issue I posted about was my audio dropping only.
The 2340's DK was holding fine at 21/2 watts (DK.) It seems as if you're having the same problem.
I don't recall what the issue was. I sent it to Mike. I'd have to look at the receipt in order to see what Mike diagnost and repaired.
I'm sure I've the receipt, but I'm not at the QTH (where the receipt is,) and won't be back there for about a month.
If you can't check tubes than replacing the two 6BQ5 modulators would make sense.
If you joined that FB Sonar page than I'd ask Mark Middelman.
He's the pages creator and the owner of that incredible Sonar collection.
I'll go ahead and ask him the question for you.
I will let you know what he thinks it is as soon as he replies to my question.