Hartke B150 Bass Amp

[Archie Speed]

Points of clarification required here I reckon. Ac power verified into transformer, no output. Infinite ohms reading across secondary. Disconnected.

Didn't mean to start a skirmish here guys. Thanks for the help.

[The Dude]

As of the power amp schematic, every manufacturer has his own preferred way of doing things.
I bet that 150W amp will be very close to the 200W one ... if not actually the same .
Get the Hartke 2000 schematic and/or the 1400 and probably you will have a useful road map.

Actually, I believe this is a little 15W practice amp. Probably has the typical TDA20(something or another) output IC. There would likely be any number of similarly built amps that would have a transformer that would work.

[The Dude]

Points of clarification required here I reckon. Ac power verified into transformer, no output. Infinite ohms reading across secondary. Disconnected.

Didn't mean to start a skirmish here guys. Thanks for the help.

No apology necessary. The skirmish wasn't started by you and we who've been here a while know well who starts most of the skirmishes. If the secondary is open, then it's toast as you already knew. Good luck in finding a replacement!

[Enzo]

So you have an open secondary? So you are now at the what else is there to lose stage. The transformer has to come out, so take it out. Note all the connections, DO NOT rely on memory. Take photos, draw pictures, make notes, tag wires.

Now look at the transformer, inside it is windings of enamel wire, so any external wires are connected inside the transformer to those enamel ones. Get into the transformer where the wires come out, you may have to do some ugly digging and cutting. Inspect the inner connections. You might get lucky and find a broken solder job on one.


If it can be fixed, great, no need to buy a new one. And if not, oh well, it had to come out anyway, and you might have learned something.

[Archie Speed]

Always learning something new. Life.

Most all of the instruments & various associated 'devices' that I get to work on are items that others consider real junk. Trying to breathe life back into 'junk' is something I find enjoyable & challenging. Low buck shop. O-scope & tone generator are apps w/homemade probes. Don't do too bad though, on days when my eyes work, my hands don't shake too much and my brain engages. I developed a reliance on schematics over a long career that used such things. Guess I'm a creature of habit with self esteem issues.

Asking for and actually getting a schematic request from any given company that plays their cards close to their vest is a crap shoot, I've found. Getting 'Qualified Tech' status can be a subjective thing, especially for a one person shop that is, essentially, a hobbyist operation. Dealers choice and I understand...kinda.

I thank you all for the input given. Here, I learn a lot. I'll burrow into this thing & see what's up. If I find something repairable, cool. If not? I'm sure that I can come up with a suitable replacement part. If not, I'll ask again and someone will help. Because you folks are really good at that very thing. My respect, gents.

[soundguruman]

Always learning something new. Life.

Most all of the instruments & various associated 'devices' that I get to work on are items that others consider real junk. Trying to breathe life back into 'junk' is something I find enjoyable & challenging. Low buck shop. O-scope & tone generator are apps w/homemade probes. Don't do too bad though, on days when my eyes work, my hands don't shake too much and my brain engages. I developed a reliance on schematics over a long career that used such things. Guess I'm a creature of habit with self esteem issues.

Asking for and actually getting a schematic request from any given company that plays their cards close to their vest is a crap shoot, I've found. Getting 'Qualified Tech' status can be a subjective thing, especially for a one person shop that is, essentially, a hobbyist operation. Dealers choice and I understand...kinda.

I thank you all for the input given. Here, I learn a lot. I'll burrow into this thing & see what's up. If I find something repairable, cool. If not? I'm sure that I can come up with a suitable replacement part. If not, I'll ask again and someone will help. Because you folks are really good at that very thing. My respect, gents.

This tranny is made by "Keen Ocean" in China.
You cannot buy one from them. They do not answer emails, either.
And, as you noticed, they burn out pretty frequently.

Which is WHY I cry all the time, about lack of support on Chinese amplifiers, especially transformers.

They do not want you to fix it. They want you to throw it in the trash, and buy another one.

IF you deal with reliable companies, they will always give you parts and schematics.
Just SKIP the ones who won't.
BUY amps from Fender, GK, Yamaha, Peavey, and many others, instead. (Japanese charges for schematics, usually)

[Enzo]

I just looked it up, the B150 is a small practice amp, sells under $100 at MF. Most companies have a do not repair list, meaning they will not pay warranty centers to fix them. it is cheaper for them to simply replace the unit for the customer. Doesn't mean they are unreliable, just means who pays what for warranty repair. BUT... That sometimes also means they are not set up to support the item. SO they don;t have schematics to hand out, for example. That MIGHT explain why someone calls them for the HA5000 schematic and gets it, but someone else calls for a B150 and doesn't.


yes, I like to have schematics myself, and many times I spend 15 minutes looking for one on my old files only to find the problem is obvious once the amp is opened. and I never look at the drawing I spent time finding.


Little amps like this, whether Crate or Peavey or Fender or Hartke, are all very much alike inside. USUALLY there is a chip amp for a power amp. That is going to be a 5-leg one like the TDA2050 or 2040. Or maybe an LM3886 with 11 legs. TDA7293 in some, but not so many of the small amps. And there are other chip amps. Some of the amps have an actual transistor power amp, but it sill be the same as a million others.


Whatever the thing uses for power amp, it will need a power supply for that power amp as well as for the preamp. The power amp will want a pair of power rails in the 25-35v range or thereabouts. The preamp ICs probably want 15v supplies, or maybe 12v. Those will eather be taken from the higher voltage with resistors and zeners, or maybe use Vreg ICs. Either should be easy to spot.

The preamp, well, a couple ICs? They have power or not at their power pins. The output pins are stuck on a power rail or not. Touching an input pin should make hum on an output pin, if the IC works.

Your amp has a headphones jack, which means a speaker cutout contact in the jack, so if the amp is silent, we check the phones jack.


All that took longer to describe than it would to check.



"Qualified Tech" is not some personal thing like a diploma from school. It means a couple things. At minimum it just means someone who does this for a living. They don't want some kid electrocuting himself poking around inside. To achieve that status with a company, you get set up to be a warranty repair station. As such, you are a representative of that company in your are - as far as customers go. The company will expect you are a real business, not just an enthusiast in his home. Most ask for photos of the outside, the shop, the customer counter, the parts storage, and the bench. Most ask for an equipment list.

In return, if you are accepted, you get the support from parts and technical as well as documentation like schematics. You get listed on the web site, or if customers call them you get the referral. To a guy like me, that factory referral is far more effective than a Yellow Pages ad. Of course there may already be an authorized shop for that brand in your area.

[The Dude]

There's also the strong possibility that, since we have a transformer with an open secondary, something else shorted causing it to burn up. Before I spent the $ to order/purchase a transformer, I'd check the output device(s), rectifier(s), etc. and make sure nothing is shorted. One could easily get into a situation where you were upside down on this amp, especially given it's value.

[Enzo]

And, as you noticed, they burn out pretty frequently.

Really? Frequently? SO far we know of this one. How many others have failed? What percentage of them?

Which is WHY I cry all the time, about lack of support on Chinese amplifiers, especially transformers.

As you have been told repeatedly, the Chineseness has nothing to do with support level.

They do not want you to fix it. They want you to throw it in the trash, and buy another one.

This is just juvenile foolishness. That simply is not how they work at these companies. In fact, under warranty, they will SEND you a whole new amp. The last thing Hartke wants - or any of the others - is for you to throw their amp away in disgust. They want you to like the little B150 so you will buy a HA3500 later when you want a real amp. You toss your B150, and you will be looking at Fender or somewhere for the next amp.

BUY amps from Fender, GK, Yamaha, Peavey, and many others, instead.

Those are all fine brands, and just like the Hartke, all their under $100 amps are made in China too.

[R.G.]

This tranny is made by "Keen Ocean" in China.
You cannot buy one from them. They do not answer emails, either.
And, as you noticed, they burn out pretty frequently.

Which is WHY I cry all the time, about lack of support on Chinese amplifiers, especially transformers.

Here we are back at China-bashing.

SGM, it's clear you have no concept how things are manufactured today, and are exposing your lack of information by your rants.

No contract manufacturing firm will ever sell parts made under contract directly to consumers. It is part of every manufacturing contract. And the clauses that enforce this are DEMANDED BY THE BUYER OF THE MANUFACTURING RUN, NOT THE MANUFACTURER.

If you have a beef with support on X brand amplifiers, BLAME THE GUY WHOSE NAME IS ON THE FRONT OF THE BOX not the company they paid to run the soldering machines.

And you have the nerve to call other people clueless. Wow.

[MarkusBass]

This is very basic 20W bass guitar practice amp. It uses most probably 2x20V transformer. Disconnect the wires from the transformer to the PC board and check voltages on the secondary winding. If there is no voltage, buy a new transformer. Between the transformer and the rectifier there are inductors - check whether they are not open. If this is not the case, buy a transformer with similar dimensions. The power rating is most probably between 30 and 40 W. It's something like 15$ on ebay. Maybe a toroid transformer can be used.

Mark

[mozwell]

B60 & B90 sch may be close enough.....

Often a power transformer will have an internal thermal fuse on the primary.
You mentioned mains voltage applied, but no secondary voltage, secondary measures 0 ohms (power off).
Please check the primary resistance as well.

If you carefully slice the insulating paper near the primary active wire, you can go down o find the thermal fuse, just short it out with a small length of wire, then carefully put the paper back & tape it all up with high temperature fiberglass tape (not electricians tape).
You can now see if you have secondary voltage under power.
BEFORE you reconnect the secondary to the amp, measure the diodes in the rectifier bridge, measure the power transistors or output IC for shorts from each rail to the speaker output.
If all is good, build & use a light bulb limiter to power this sucker up !

[Jazz P Bass]

Good advise on the troubleshooting.

IF the internal fuse is blown & a jumper across it brings it back up, I would suggest that the transformer be replaced.

[The Dude]

B60 & B90 sch may be close enough.....

Often a power transformer will have an internal thermal fuse on the primary.
You mentioned mains voltage applied, but no secondary voltage, secondary measures 0 ohms (power off).
Please check the primary resistance as well.

If you carefully slice the insulating paper near the primary active wire, you can go down o find the thermal fuse, just short it out with a small length of wire, then carefully put the paper back & tape it all up with high temperature fiberglass tape (not electricians tape).
You can now see if you have secondary voltage under power.
BEFORE you reconnect the secondary to the amp, measure the diodes in the rectifier bridge, measure the power transistors or output IC for shorts from each rail to the speaker output.
If all is good, build & use a light bulb limiter to power this sucker up !

I absolutely do not recommend this! That thermal one shot is in there for a reason. Absolutely do not "short it out with a small length of wire" and continue using the transformer. As I said in a previous thread, a tech from my city did this and caused an apartment fire. He was sued for damages and lost. It's just a bad idea to post this on an open forum that many novice users read.

And, besides, the op said that the transformer primary was ok.

Edit: At the very least replace the fuse. They can be easily had. DO NOT just jumper across it. That said, for the average Joe, I still think it a bad idea to even bring up the idea of digging into a transformer.

[mozwell]

Dude
I agree, in my incomplete post above, I omitted "so you can check the secondary voltage, in order to see what transformer you need to replace it with"
This bypassing a thermal fuse can get you going to check if there are any other problems, and if not, you have enough information to replace the transformer.
If the thermal fuse has gone, the transformer has gotten fairly hot inside & degraded the insulation system, it may be a shorted rectifier on the output of the transformer, or some other problem, that has caused the transformer to overheat without taking out a supply fuse......

I would never send a repaired unit out with a transformer like this, this is just a way of "very temporarily" being able to keep troubleshooting, preferably with a bulb limiter in place....