5F1 Built 6V6 issues (Sparking on tube)

[Mojojtm]

Hey All,

I recently built from a kit a 5F1 Fender Champ a very simple circuit if compared to other build such 18 Watts or 15watts Madamp Amp.

I am 100% sure to have built the circuit properly I have no doubts but when turning on the Amp I get sparks on 6v6 Tube the Amp indicator light turn on, there is also frying noise but I have switched the amp immediately off.

After some troubleshooting I realized the OT is blown

Apparently was sent already blown since from the moment i finished the built it never worked properly.

Now vendor is claiming that could have been damaged by building it wrong but that is not true the build is correct and I am 100% sure of that.

What could most commonly cause an OT to blow?

I know is correct because I returned the kit for the vendor to check, they also confirmed the Amp is correctly built and they confirmed the tube is also fine and they also confirmed the issue is blown OT.

I am asking you here this question to self defense myself in case they came back to me saying I did something wrong, something that I couldn't maybe rebate due to possible limited knowledge even though so far I built few 18 Watts one 15 Watts Madam Amp which are far more complex.

Now how can I also demonstrate if required that the OT was blown out of the box? I know it was.

Somebody told me on 5F1 the 6V6 Tube and the 5AR4 obviously have the same pins connections therefore swapping by mistake could cause an OT to be blown, I don't think I have made such a mistake but could that be true?

Thanks

[Stevem]

You have something else wrong because a shorted output transformer will not make a tube arc over internally or externally at the socket.

I have replaced about 50 plus shorted output transformers in my life and never have I seen what you are assuming and posting about take place.

Can you post up some good close in shots of your builds power supply section and output section please?

[Mojojtm]

Well I had your same doubt

Unfortunately even the vendor confirmed the same that the OT is blown but the circuit was correctly built. Now of course logically I thought about the same as you mentioned, something else must be wrong, but I have reviewed the Amp 10 times and rechecked all connections, soldering points, and I couldn't find anything wrong, therefore I assume that the built was correct and the fact that the vendor confirmed the same reassured me that I was not wrong.

What to say atm the Amp was sent back to the vendor here in the Netherlands and they have said to investigate how come that the OT was blown, it seems that was actually sent out with the kit already blown, I can't possibly explain the lighting sparks on tube, (inside the tube glass) with some sort of light hiss noise, however as mentioned earlier never kept the amp on for more than 15 secs as soon as the lighting was seen it was unplugged.

Another thing to add the bulb current limiter didn't reveal and shorts the bulb light didn't glow bright which is a sign of no short

I have some photos taken previous sending the Amp back let me see if I can post them in here

[TUBEDUDE]

Bad tube also, likely not related. Hard impacts can short the tube internals, especially if the tube is still hot.

[Mojojtm]

Hey all

I have attached photos of the Amp those are prior the amp was sent back.

Now the vendor is saying that there were few solder points loose those are the cause of sparks and OT blown

It is strange but what to say

They showed me some pictures of the actual problem but honestly unsure if the photos are of my amp

There is one resistor soldered on top of the turret that is missing solder completely and that doesn’t show to be the same on the photos I posted here.

Anyway what can I do , probably pay for the new OT and ask them to fix the soldering.

What is strange is that I built 3 amps in the last 3 months and 4 more amps last years all 18 watts or Madamp and those are far more complicated and never had a single issue

Thanks

[Phil_S]

They showed me some pictures of the actual problem but honestly unsure if the photos are of my amp

I find it hard to believe that a reputable vendor would do such a thing, but anything is possible. It might be worthwhile to send them pictures of your amp showing what you believe to be the same areas and point out the differences. Maybe ask them if they confused your amp with another amp? I'd be very careful to be polite and not to accuse anyone of anything. You'll catch more flies with honey than you will with vinegar.

You might consider posting here the pictures they sent you. Maybe you'll get a second opinion on whether it is the same amp.

[Mojojtm]

They showed me some pictures of the actual problem but honestly unsure if the photos are of my amp

I find it hard to believe that a reputable vendor would do such a thing, but anything is possible. It might be worthwhile to send them pictures of your amp showing what you believe to be the same areas and point out the differences. Maybe ask them if they confused your amp with another amp? I'd be very careful to be polite and not to accuse anyone of anything. You'll catch more flies with honey than you will with vinegar.

You might consider posting here the pictures they sent you. Maybe you'll get a second opinion on whether it is the same amp.

Yes I'm with you I already replied to them politely, also I can't be 100% sure it is hard to just judging out of some pictures and I told them also if maybe the Amp was swapped by mistake. It is a reputable vendor, the only Vintage amp seller and amp kit seller in the whole Netherlands therefore I doubt they did something dodgy.

It could be instead very much possible that the Amp, a very common one sold on daily basis, that was swapped with another customer amp.

Let me send the other pictures for the vendor pointing to the unsoldered points in various parts.

The seller also said:

"Our amp technician came across some problems with the soldering in the amp. A few cold joints / bad connections in the amp. Turret (only some loose solder on the top of the turret), tube socket 6v6 (anode wire had bad/loose contact) and the output jack for instance. The output jack had a loose soldering contact on the 4 ohm tap. Some points were not or not sufficiently pre tinned and the green 4 ohm tap wire was not stripped right. Just 2 or so of the wire strands made contact. Our amp technician has made some pictures but it's hard to get it on camera. According to him all this could result in some unwanted fireworks and can cause the OT to fail."

I found hard to accept it since on all my other builds never had a single issue. However I admit that it was built with a speed to finish quickly the amp, and I noticed that the solder used was one of those Eco solder that lacks in quality that might be the real culprit perhaps.

[Mojojtm]

Adding here photos from Vendor Technician claiming that the faulty OT was caused by lose joint soldering.

However those pictures do not seems to be exactly matching the picture of my real amp compare previous phots sent, (Original Amp "mine") with the one below here sent out from vendor.

If you check below photo with turret without solder and if you check my photo sent earlier, my amp is showing all turrets soldered including the one shown here below.

[Phil_S]

I'm no expert. I would say they sent you a picture of the amp you sent them. Look at the first pair of turrets with the bent wire on the cap and the mended lead on the resistor. These are identical. I suggest there was a bad solder on that turret that fell off when the package got thrown around during shipping. Also, for the unsoldered turret, the yellow barrel cap has the identical orientation and positioning as the original picture you posted.

[Mojojtm]

I'm no expert. I would say they sent you a picture of the amp you sent them. Look at the first pair of turrets with the bent wire on the cap and the mended lead on the resistor. These are identical. I suggest there was a bad solder on that turret that fell off when the package got thrown around during shipping. Also, for the unsoldered turret, the yellow barrel cap has the identical orientation and positioning as the original picture you posted.

Yes ok thanks buddy I agree

There is something to say I ran out during the building if the 5F1 of my usual solder and used some sort of ecological solder that I had as spare, probably that us the reason of cold joint.

[Phil_S]

Yeah, no one seems to like the new stuff. I was using 96% tin 4% silver, but can't seem to find it in the smaller tubes I like to buy. I had no problems with the 96/4 mix. The solder with Silver, Tin, and Copper, in my experience, is hard to use and should be avoided.

[kraml]

On the far left, the alignment of the cap to the resistor and the shaping of the leads on the cap are different in the two pics.