HT5 power tube distortion and other concerns

[Laimac]

Hey guys. Just keeping you updated on things... So it turns out my HT-5R suffered from the well-known "R39 failure" - apparently a relatively frequent issue. As it was being fixed I took the opportunity to order some RCA NOS 12BH7 for the power amp to complement my new NOS 5751 in the preamp. Because I am really lucky recently I asked the tech to look at the bridge pickup of my LP Studio that never sounded good and he rightfully diagnosed a defect there too...
Well when life gives you lemon... I decided to take the opportunity to replace the complete set of Gibson 57 Classic / 57 Plus with SD Pearly Gates and also turn the Gibson "tuned coil tap" system (a cheat that uses a resistor to suck part of the frequencies - caveat emptor: I am no electronics specialist so don't bite if I am explaining it wrong) with a proper coil split. Because the rig was out of action for a while and I always hated the Celestion 70-80 in my cab, I also placed an order for a Scumback H75... Don't go thinking I am rich but I always had the intention of getting myself a solid basic rig then upgrading it and now was as good a time as any.
I am due to get the whole thing back on Sunday but the tech already tested the amp and said it sounds great. He says "better tone, cleans are cleaner and sweeter, overdrive less noisy and on full gain and volume no squeal" (TBH I never got to dime it before but that al sounds promising).
I cannot wait to hook it to the upgraded LP and the Scumback!
Will keep you posted on results.

[thephantum]

The "R39 failure" is actually a PCB issue. Some PCB's manufactured in early 2009 had a defect (specifically a short) that caused R39 to burn out. I wouldn't say it's a frequent issue but, aside from tube failure, it is about the only thing that would cause an HT-5 to land on a bench...so I can see why a tech would say it's frequent.

Do you know what year the RCA 12BH7 is? Just curious....

[Laimac]

Yes, it's apparently a short from the MOSFET causing the two nearby resistors to heat up and either burn or desolder. It does seem relatively common. Anyway the tech decided to make a quick video (https://youtu.be/iSrQEPKTlZw) when fixing it.

Regarding the tubes, I got a set of three and the markings were quite faded but it seems two were shipped in 66 and one in 67. Not sure which one he put in the amp. Looking forward to picking up the rig tomorrow.