[GoneToPlaid]

My Tube 02 pro just recently wont output to RCA out, only headphones. Anyone else experience this? Ive opened it up and resoldered any questionable solder joints etc. Im thinking its in the Mute circuit possible. Ive tried unplugging it basically any normal tricks to stuff like this and still no sound from RCA out.

The heater filaments for the left and right tubes are wired in series. If the filament in either tube burns out, then there will be no audio output for the RCA outputs or for the headphone output jacks. Check and confirm that there is not any audio output for the headphone output jacks. If there is no audio output for the headphone output jacks, then the filament in one of the tubes has burned out. Since the tube filaments are wired in series, if one filament burns out then there will be no audio output for both the left and right output channels. It is advisable to buy a matched pair of replacement tubes.

The Tube 02 Pro comes with GE JAN 5725W tubes. The instructions for the Tube 02 Pro state that the tubes can be replaced only with 5725 tubes. This is incorrect since the circuit board of the FX-AUDIO TUBE-02 PRO connects Pin 2 and Pin 7 for each of the tubes. This effectively connects pins 2 and 7 to the cathode, grid 3 and the screen in the tubes. The result is that the sharp cutoff pentode feature of the 5725 tubes is disabled such that the 5725 tubes behave exactly like 5654 tubes.

You can replace the original GE JAN 5725W with a matched pair of GE JAN 5654W tubes or a matched pair of Russian Voskhod Rocket 6ZH1P-EV or 6*1N-EB or 6J1P-EV tubes. I do not recommend the Russian tubes since these tubes are subject to ringing and to electromagnetic RF interference from sources such as amplified speakers, wireless keyboards, wireless mice, cell phones, et cetera. Instead, replace the tubes with a matched pair of GE JAN 5654W tubes. I have been using GE JAN 5654W tubes with my Tube 02 Pro for over two years. Simply search for "5654w vacuum tubes" on Amazon and order a set of tested and matched pair of GE JAN 5654W tubes.

 

[Gaspar74]

HI, Yes maybe I should of been clearer. Headphone outputs work fine, Just not the RCA Line out.

 

[GoneToPlaid]

The HSD4/5-S signal relay (it is the white colored block shaped thing on the circuit board just below the RCA output jacks) probably has burned out. The purpose of this relay is to prevent a popping sound on the RCA output when you turn on the Tube 02 Pro. The /5 in the part name indicates that this is a 5 volt relay (5 volts for the relay coil).

I found this relay on Amazon and for much cheaper on Aliexpress. Here are the links:

https://www.amazon.com/5pcs-Type-HFD4-5-S-HFD4-005-S-Relay/dp/B08RB2VD6S

https://www.aliexpress.us/item/3256805986784737.html

 

[GoneToPlaid]

There are five of these HFD4/5-S relays on the Tube 02 Pro circuit board. They are the cream colored rectangular blocks in the photo.

 

[Gaspar74]

TY, Yes I was thinking exact same it was one of those relays. I have some however 12v or 24v relays. Im going to order and give it a go. Thanks

 

[Gaspar74]

Managed to get one for RCA out off hot air worked great. Looking see if I have comparable. Wonder if I can just jumper it for now as in by pass the relay

 

[Gaspar74]

Temporary fixed it, bypassed the relay. Im using it only as a preamp, BUt Im going order the correct relay now and I can use it. Thanks for reconfirming what I had thought issue was.

 

[GoneToPlaid]

Temporary fixed it, bypassed the relay. Im using it only as a preamp, BUt Im going order the correct relay now and I can use it. Thanks for reconfirming what I had thought issue was.

You are very welcome.