New HT5-R - No Sound!

Discussion - HT-5 amplifiers.
Rosspj15
Posts: 8
Joined: Sat Aug 18, 2012 12:00 am

Mon Aug 20, 2012 9:22 am

It does look that way to be honest. After looking through the web the problem comes up alot not just on this forum either. Have really lost faith in these amps now they seem to just give up after a few months of light use and i really look after my amps. The same issue has just been raised again on this forum last night. I hope black star recognise they have a problem and give us some information.

RCB-CA-USA
Posts: 81
Joined: Mon Apr 09, 2012 12:00 am
Location: United States of America

Mon Aug 20, 2012 12:52 pm

Enquiry Type: Technical Help

Message:

Hello! I own a Blackstar HT-5RH and an HT-408. There is no sound coming out of the 408 speakers from the clean channel but there is a faint signal coming from the gain channel. The emulated out works fine on both the clean and gain channels. Is there anything thing I can do to trouble-shoot and fix the problem (re-seat valves, replace the tubes or fuse, etc.)? Thank you!


Thanks for your enquiry!

I have forwarded on your message to our US Distributor, Korg USA, who will aim to reply to you within two working days.


RCB-CA-USA
Posts: 81
Joined: Mon Apr 09, 2012 12:00 am
Location: United States of America

Mon Aug 20, 2012 4:11 pm

Update:

I contacted Korg USA. Korg said there's an authorized repair shop locally. I'll post an update as as soon as I get one.

...a day without Blackstar is like a day without sunshine... Image

Rosspj15
Posts: 8
Joined: Sat Aug 18, 2012 12:00 am

Mon Aug 20, 2012 10:09 pm

Yea keep us updated will be interested to see what they say the fault is.

Rosspj15
Posts: 8
Joined: Sat Aug 18, 2012 12:00 am

Wed Aug 22, 2012 10:21 pm

Well it's fixed and it was a very strange one.

Hope you don't mind me posting again but I have browsed this forum for a long time and it has always helped me out so I hope this helps a few people out in the future.

So changed the MOSFET no change at all which thought was very strange as when I buzzed it it was shorting out. So took the new part off and buzzed the pcb and to my surprise there was a short on the actual pcb itself. So after taking some resistors out to narrow down the problem it was still shorting. So it could only be one thing a short on the actual board which I have never seen before. So put the board under the microscope and sure enough you could see a faint arc line on the pcb between the two holes where the MOSFET goes.

The reading between the two point was 6k a very strange reading so decided to drill a 0.8mm hole between where the two prongs go. Measured across the two again and sure enough the short had totally gone.

So in short a fault on the board was to blame I don't know why the board failed maybe there was a spike may be a fault in the board. I would think a fault in the board as reading through the bs forum people have experienced similar symptoms and all bought there amps around January this year like mine so could have been a bad batch of boards.

So if you have similar problem I would send it back but as I didnt want the hassle and my amp being thrown around the country I done it myself but only because I knew what I was doing sort of lol.

Any way it is now fixed and have played it for a few hours now and sounding better than ever just glad to have it back.

I have wrote this in first person but it was a friend of mine at work who done most of the work and is the clever one so sorry if it doesn't make complete sense but I hope it does.

Any technical questions fire away and will ask my friend he knows most things about electronics.

So if you have burnt out resistors r39,38or even 10 it could be because of this short.

I hope this helps people understand a problem when it arises especially if it is out of warranty.

Any thoughts would be great cheers ross.

jaded faith
Posts: 3
Joined: Wed Aug 22, 2012 12:00 am

Wed Aug 22, 2012 11:56 pm

Hello there,

My name is Rob and I am new to this forum. I am the owner of Jaded Faith Mods, an amp modification/service/repair company based in New Jersey. I stumbled upon this post researching an issue with a customers amp and I was hoping to get a little additional info from you.

Upon opening the customers HT-5 on my bench (no sound), I immediately noticed R39 was burned up and provided no resistance reading. Referencing the schematic, this is one side of the solid state PI circuit in this amp. I too found all surrounding parts to appear fine and reading as they should. However I did have a sneaking suspicion regarding TR3 (an IRF830 MOSFET), which connects to R39 on that side of the PI circuit. Even after replacing R39, there is enough heat being generated at the rear-most solder pad to actually melt the solder. There has to be a short somewhere.....

Is this the part where you found the short described in your last post? I have a feeling this amp has the exact same issue. I'm going to go test this right now and look forward to your reply.


jaded faith
Posts: 3
Joined: Wed Aug 22, 2012 12:00 am

Thu Aug 23, 2012 1:30 am

Update:
The post regarding drilling out the area between the pads for TR3 worked and the amp is now back to life. For those interested, there are shorts present in the PCB and this fix will work. Do keep in mind this is a likely from a batch of faulty PCB's and the manufacturer is probably aware already. This is not a simple fix and I would recommend contacting them for the recommended course of action. If you prefer to go to a trusted tech or shop, this will work.

If R38 is the blown resistor, the problem is with TR2. If R39 is blown, it is TR3. It is entirely likely R10 could go as well and it is connected to both R38 and R39.

Hope this helps,
Rob

Rosspj15
Posts: 8
Joined: Sat Aug 18, 2012 12:00 am

Thu Aug 23, 2012 10:40 am

Hi mate

Glad you got your issue sorted too. Glad it was not just my amp and is def looking like a bad batch of pcbs are to blame for this problem. I am very surprised backstar have not recognised this issue as it seems a very common issue. You would have thought they would inform there retailer network of the fault with instructions on how to fix it so people can have them fixed at place of purchase instead of having the hassle of sending it away and have it thrown round in the back of lorry.

As you said Rob i think bs must be aware of this issue but they seem to be just waiting for them to go wrong instead informing people that there is a known problem.

Glad my post made sense and sounds like there is going to be a few more amps with this issue arise yet.

Ross.

jaded faith
Posts: 3
Joined: Wed Aug 22, 2012 12:00 am

Thu Aug 23, 2012 12:45 pm

Ross,
I agree completely. Most of my work is on the Randall and Egnater MTS line of amps, but I work on all makes and models of amps. I have seen these types of issues on some poorly made cheaper PCB's in the past. It's an odd thing to look for as a tech, as you typically have faith in the PCB and it's not a top-of-mind troubleshooting thought. I once had a similar issue with a Marshall 1959RR Randy Rhodes Sig Head and it was maddening to track it down.

After repairing the amp, I highly doubt it would be a recommended repair from BS. I am an Authorized Service Center for many manufacturers and I would think swapping the PCB with a new one would be the ideal course of action. Doing this repair properly requires a lot of skill and there is potential for big problems if done poorly. There is around 330V present at that part of the circuit when working correctly.

On a positive note, the amp is up and running and I think it sounds fantastic! This was my very first time playing a BS amp and I was very impressed with the tone. I was a little hesitant before it fired up based on all the solid state circuitry present (nearly the entire OD channel is SS), but it was a shining example of how good SS can sound when done right. I am seriously considering adding something from their line to my personal collection.

All the best,
Rob

Blackiemore
Posts: 2
Joined: Thu Jul 19, 2012 12:00 am
Location: Far Beyond The Sun

Thu Aug 23, 2012 5:13 pm

Update:

I went back and forth for weeks with Sweetwater trying to get my BS head replaced. The delay from the factory pushed it to 6 weeks! Finally I made the decision that there was a considerable amount of risk in reliability of the HT5RH so I requested Sweetwater exchange the amp for an Egnater Tweaker. I really think that the BS sounded good and the OD channel was sick, but IMHO the amp was under powered and not as versatile as I would have liked. I also wondered if Blackstar is as invested in the HT line as they are in the premium amps they build. I’m pleased as punch with the Egnater though. Image

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