Blackstar HT-5H no working

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jungle-jim
Posts: 1
Joined: Wed Sep 28, 2022 9:29 pm

Wed Sep 28, 2022 10:42 pm

Hello
I have a Blackstar HT-5H which has been a really nice amp for the years I have had it, but is now no longer working, and just makes an intermittent static sound (though it does still work as it should out of the headphone jack).

The only possible event I can think of which has caused this failure was: sometimes my son plays a bass guitar through it *quietly* at less than bedroom volume - which hasn't yet caused a problem over several years - but him playing bass through it was the last time I can remember the amp working, so that's why I'm mentioning it.

I have taken the circuit board out - it's not got the damage around the TR2 and TR3 FETs or the R38, R39 resistors as some posts in this forum have previously discussed - though the traces around this area are a bit yellow like they've been getting hot.

The tubes seem to be ok visually - the 12BH7AEH Electro-harmonix lights up on both sides at the top when switched on, and the TAD 7025 also seems to glow.

And as I said it works through the headphone jack - guitar signal comes into the headphones nicely with the tone as you would expect.

The separate speaker - which I can't test with another amp (haven't got one handy) - I think is OK - it measures 13ohm across it, it's rated as 16ohm.

The version of the main board in this unit denotes that it's 'Issue 3' of HT-5_ELEC_ARTW_00. The barcode on the back says 2009 02EC0177 (if this indicates the year). I have had this amp 3-4 years, but it's in as-new condition - it hasn't had a hard life.

All the electrolytic caps on the board look ok - not bulging. Most of the larger ones are Nover.

There's some soldering on this board which is a bit blobby - I could go around and re-do a lot of the worst looking ones, but it did work for years despite this...

Thanks for reading this - this is the beginning of trying to diagnose this problem, and I've said what I've got so far. I am an intermediate-level amateur.

But - if it was the bass guitar - what would be the likely consequence of too much low frequency input? What would that damage? It definitely was not played loud at all with the bass, and speaker wasn't pushed, but there may have been low frequencies that still did damage somehow. This might be a place to start.

Again, thanks for looking at this, any thoughts or suggestions appreciated.

Kamay
Posts: 1
Joined: Mon Oct 02, 2023 5:25 pm

Mon Oct 02, 2023 5:27 pm

Decided to try playing silently through headphones. Plug them in, only get external sound. Think maybe I have to unplug the speakers. Then I get no sound at all. Tried the switch between 1W and 5W, did nothing. Is there something blindly obvious I’m missing as to why this isn’t working? Do you have any ideas? geometry dash lite

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